step up, snap ya back
A huge Special Defense stat, decent Attack, and a massive movepool give lots of reason to use Kecleon. With a RestTalk set, Kecleon has a lot of staying power, and on the offensive Kecleon can be pretty difficult to switch into. Unfortunately, the chameleon falls pretty short of being an "NU Snorlax." Color Change is a huge mixed bag of an ability, and while it works in Kecleon's favor sometimes, more often than not it gives the opponent a work-around to break it faster. Most of the special attackers in the tier carry moves that are super effective against their STAB move or vice versa, and Kecleon's low Defense means most physical attackers just blow right through it. In the end, Kecleon is great on support and forms one of the most potent defensive cores in the tier with Relicanth and Chimecho, but don't expect it to "one-man army" the opponent.
name: Specially Defensive
move 1: Body Slam
move 2: Thunder Wave
move 3: Protect
move 4: Shadow Ball / Brick Break
ability: Color Change
evs: 252 HP / 4 Atk / 252 SpD
Kecleon is one of the best blanket checks to special attackers in NU, and this set is designed to take advantage of that fact and spread paralysis for the rest of its team. Kecleon fits best on balanced teams as a role compressor, forming a two or three Pokemon defensive core. Body Slam makes use of Kecleon's decent Attack stat and hits most of the specially offensive Pokemon in the tier in their weaker Defense stat. Protect allows Kecleon to scout moves, which is particularly helpful in Kecleon's case as it allows you to more accurately predict how your opponent will play into Color Change. Shadow Ball is recommended to fill out the set since Kecleon is one of the best answers to Haunter in the tier and it gives Kecleon something to hit Sableye with. Brick Break is a good alternative to prevent Mawile from being able to use Kecleon as complete setup bait, and it gets a decent hit on Glalie and Dewgong.
Kecleon's movepool is huge, so there are a lot of different ways you can customize this set to suit your needs and which Pokemon you need to more reliably counter. Most prominently is Kecleon's huge array of coverage moves that can fill the last slot to allow it to cover certain weak points in your team structure. Icy Wind is a great option on Kecleon to slow the opponent down to potentially stop a sweep and get a decent hit on Pupitar, Tropius, and Tangela. Fire Blast allows Kecleon to counter Bellossom and Tangela even in the sun, as long as it avoids Sleep Powder. Hidden Power Grass can be a nasty surprise for Whiscash and Relicanth thinking they can absorb Body Slam and Thunder Wave safely.
Kecleon works best as part of a defensive core as its Defense stat is pretty lacking, leaving it very vulnerable to physical attackers like Hitmonchan, Pidgeot, and Raticate. Relicanth and Chimecho pair extremely well with Kecleon, and as a core they cover nearly every major threat in the tier between them. Relicanth in particular appreciates Kecleon's ability to absorb most Grass-type attacks, and Chimecho loves Kecleon's ability to paralyze the opposing team. In return, Relicanth easily stops Normal-types in their tracks and Chimecho switches into Hitmonchan's Fighting-type attacks. In general, Pokemon that will appreciate Kecleon's paralysis support make the best teammates, in particular slower, bulkier sweepers such as Swords Dance Tropius, Bulk Up Hitmonchan, and Bulk Up Vigoroth.
move 1: Seismic Toss
move 2: Toxic
move 3: Rest
move 4: Sleep Talk
ability: Color Change
evs: 252 HP / 4 Def / 252 SpD
This set is better designed for heavy stall teams, making the absolute most of Kecleon's huge Special Defense stat to counter certain special attacking threats throughout a match, including even Huntail. Seismic Toss and Toxic allow Kecleon to inflict the most damage possible over an extended match, preventing Kecleon from being complete setup bait to any Pokemon apart from some Substitute users such as Wailord and Whiscash. RestTalk gives Kecleon a ton of longevity, making it very hard to break for weather sweepers and opposing stall teams in particular. With a RestTalk set, Kecleon is less susceptible to its Color Change being taken advantage of by the opponent, as the recovery helps cover most mispredictions and surprise coverage moves by special attackers.
[ADDITIONAL SET COMMENTS]
This set should focus completely on Kecleon's Special Defense in order to best counter the special attackers in the tier throughout a match. As RestTalk Kecleon should only be used on stall teams, it should have teammates to cover its lower Defense stat. While Kecleon has no trouble walling most special attackers like Haunter, Plusle, and Bellossom, Kecleon has some major issues with mixed attackers and setup sweepers that can take advantage of its offensive impotence like Substitute Whiscash and Calm Mind Chimecho. Stall staples such as physically defensive Swalot, Roar Wailord, and Chimecho in particular make good partners for Kecleon for this reason. Chimecho stands out for being able to check Hitmonchan and can carry Heal Bell to wake Kecleon more easily. As a stall team member, Kecleon appreciates Spikes support from Roselia and Glalie to more quickly wear the opponent down with Toxic and Seismic Toss. Rapid Spin Hitmonchan also makes a good teammate to clear Spikes from its side of the field and ensure that Kecleon can more reliably check Huntail and other power special attackers throughout the match.
name: Choice Band
move 1: Return
move 2: Shadow Ball
move 3: Brick Break / Focus Punch
move 4: Trick
item: Choice Band
ability: Color Change
evs: 252 HP / 252 Atk / 4 Spe
Kecleon stands out as a Choice Band user by possessing a ton of natural special bulk, allowing it to simultaneously check special attackers and threaten the opponent offensively with its strong physical moves. While Kecleon has rock-bottom Speed as a Choice Band user, meaning it likely won't be able to sweep the opponent, it makes up for it by checking many Pokemon other similar Choice Band users, such as Pidgeot and Raticate, cannot. Return is the recommended STAB move as Kecleon will likely be taking a lot of damage from the opponent due to its low Speed, meaning the recoil from Double-Edge is undesirable. It should be noted here that Kecleon is unlikely to keep Return as its STAB move if it switches into a special attackers' attack, so another move of your choice can easily fit this slot. Shadow Ball and Brick Break pair with Return to give Kecleon perfect neutral coverage and nail the Ghost-, Steel-, and Rock-types that can switch into Return for free. Focus Punch is a decent alternative to Brick Break if you feel you can predict well due to its sheer power, but mispredicting can spell doom for Kecleon or its teammates. The last slot is reserved for Trick, which is nearly unique to Kecleon in NU. With Trick, Kecleon can completely cripple Sableye or another stall staple, such as Wailord, for the rest of the match, giving Kecleon a huge niche over other similar Choice Band users.
Kecleon is so slow that there's not much point in running any Speed, otherwise you'll end up detracting too much from its bulk or Attack. Although, if you really want Kecleon to outspeed minimum base 50s, 84 EVs can be moved from Attack to Speed. Kecleon has a few other physical moves to choose from if you want to target specific threats on the opponent's team. Aerial Ace can make for a very nasty surprise for Hitmonchan and Tangela, Rock Slide will put the hurt on the Fire- and Ice-types that Kecleon can switch into easily, and Iron Tail will hit Rock-types significantly harder than Brick Break. A Lonely nature can be run with Ice Beam or Hidden Power Grass as well to get a very strong hit on Tangela, Graveler, Shelgon, and Relicanth with the appropriate move.
Choice Band Kecleon fits best on balance teams that want an offensive switch-in to special attackers in the tier in order to keep up offensive pressure and not give the opponent an opportunity to set up. Good offensive teammates to pair with Kecleon include Relicanth, Murkrow, Tangela, and Pikachu as they have low Special Defense and lure in the special attackers that Kecleon can use to fire off strong attacks. Vigoroth in particular can make an effective teammate with Kecleon to clean up once the opponent's Normal-type counters have been revealed and weakened. Kecleon is very easily revenge killed due to its low Defense and Speed, meaning a physically bulky teammate that can pick up its slack is a recommended teammate. Offensive Chimecho is a good example that can switch into Hitmonchan easily, and offensive Mawile can keep up momentum with Baton Pass and check the Normal- and Flying-types that will target Kecleon's Defense.
move 1: Substitute
move 2: Focus Punch
move 3: Return / Toxic
move 4: Shadow Ball / Toxic
ability: Color Change
evs: 252 HP / 252 Atk / 4 Spe
Kecleon can put a SubPunch set to particularly good use as it naturally forces many switches and most of its typical switch-ins do not want to eat a Focus Punch. Kecleon can force out many special attackers, such as Haunter, Roselia, Plusle, and Flareon, and proceed to set up a Substitute; from there, Kecleon should nail the incoming Pokemon with the appropriate coverage move. Kecleon is unlikely to keep STAB on Return should it switch into a special attackers' attack, so another physical move of your choice or Toxic can easily fill this slot. Toxic is Kecleon's best move for Sableye which will likely switch in once Kecleon uses Substitute in order to absorb Focus Punch. Shadow Ball allows Kecleon to easily take out Haunter and gets a decent hit on Chimecho as well.
84 Speed EVs can be run to outspeed minimum Speed base 50s, but Kecleon wants as much bulk as possible to keep a Substitute intact against as many special attackers as possible. Body Slam is a decent alternative to Return that allows Kecleon to spread paralysis on the opponent's team and can combine with Kecleon's wallbreaking potential of Focus Punch to make it even easier for a slower teammate to sweep late-game. In the same vein, Thunder Wave can be used in place of Toxic. Icy Wind can be used to slow an opponent's switch-in down to make switching in a teammate more easily, as well as getting a decent hit on defensive Grass-types like Tropius and Tangela.
SubPunch Kecleon fits best on balance teams as a lure and wallbreaker to make it easier for a teammate to sweep late-game. Kecleon's common switch-ins include Rock- and Steel-types which will take a ton of damage from Focus Punch, and with them weakened a teammate such as Pidgeot and Raticate can sweep much more easily. Kecleon also typically lures in Hitmonchan and Focus Punch will deal upwards of 75% to Choice Band Hitmonchan, easily opening up a sweep for Pupitar or Vigoroth. Other Pokemon that appreciate Kecleon as a teammate include those that are weak to special attackers such as Choice Band Relicanth, Swords Dance Mawile, and Sunny Day Tangela.
Kecleon's movepool is very large, making many different kinds of sets possible that have not been listed above. A straight special attacking set can make use of Kecleon's huge special movepool, although it's a bit outclassed by Wigglytuff due to its higher Special Attack. However, access to Blizzard, Ice Beam, Thunder, Thunderbolt, Fire Blast, Flamethrower, Hidden Power Grass, Feint Attack, Water Pulse, and Psybeam make Kecleon very unpredictable and tough to switch into. Screech can be used to greatly increase the damage of Kecleon's physical moves, but Kecleon is too slow to really make the most of it.
Of particular note is Kecleon's huge array of supportive moves that have not yet been mentioned. Kecleon is probably the best user of Psych Up in the tier as it can easily switch into a Calm Mind-boosted Sableye or Chimecho and steal the boosts, making it nigh-unbreakable on the special side. Skill Swap is pretty gimmicky, but it can really screw over something like Flareon that can then become unable to even scratch Kecleon. Magic Coat can prevent Kecleon from being inflicted by status and bounce it back at the opponent, but RestTalk is a better method overall of preventing status from crippling Kecleon. Sunny Day and Rain Dance can be used to support the team, and Kecleon can offensively take advantage of Sunny Day with Fire Blast and Solar Beam, and can use Thunder and Water Pulse with Rain Dance. Finally, Kecleon can use Trick with something like Macho Brace to cripple the opponent without having to use a Choice Band.
[Checks and Counters]
Mawile is probably the safest switch-in to Kecleon as it takes little from Kecleon's STAB moves, is immune to Toxic, typically doesn't mind being paralyzed, and lowers Kecleon's Attack with Intimidate. In return, Mawile really only fears a boosted Focus Punch or the uncommon Fire Blast. Similarly, Metang can pretty easily switch into Kecleon and target its lower Defense stat with Meteor Mash and Earthquake. Rock-types such as Relicanth and Sudowoodo will not appreciate being hit by Toxic, but can also absorb Kecleon's Normal moves and nail Kecleon with a strong Rock Slide. Hitmonchan has a tougher time switching directly into Kecleon, but can easily OHKO Kecleon once in with Sky Uppercut. Most strong physical attackers such as Raticate, Kingler, Piloswine, and Pidgeot can easily O-2HKO Kecleon with the appropriate move. In general, many Pokemon can take advantage of Kecleon's Color Change by changing it into a type that's weak to their coverage moves. For example, Huntail can nail Kecleon with Hydro Pump and follow up with a super effective Hidden Power Grass and proceed to follow that up with a super effective Ice Beam. Other attackers that typically carry a move super effective to their own include Flareon, Bellossom, Pikachu, and Whiscash.