Swellow

Guts
Attack is increased 50% when hit with a status move.
Type Tier
Normal / Flying BL
Statistics
Min- Min Max Max+
HP
60
- 261 324 -
Atk
85
185 206 269 295
Def
60
140 156 219 240
SpA
50
122 136 199 218
SpD
50
122 136 199 218
Spe
125
257 286 349 383
Name Item Nature

Choice Bander

Choice Band Jolly
Moveset EVs
~ Aerial Ace
~ Return / Double-Edge
~ Hidden Power Fighting / Hidden Power Ground
~ Facade / Sleep Talk
4 HP / 252 Atk / 252 Spe

Standard Choice Band user. Facade is to take advantage of Swellow's Guts ability, making a burned Swellow a definite force to be reckoned with, but Return / Double-Edge do damage without being statused. Works well in tandem with Medicham, as Medicham takes out Rocks and Steels, as well as resisting Rock (although it can only take one or two hits before going down, anyway). Medicham also lures out Weezing and Dusclops like no other, so you can switch to Swellow to absorb the Will-O-Wisp and sweep their team (you'll probably want to switch out of Dusclops, though, to save this Swellow for the end-game, and just work on weakening Dusclops to sweep with Facade). Quick Attack can go over one of the Normal moves for those Salac + Flail / Reversal users. Hidden Power Fighting is primarily for Tyranitar, Hidden Power Ground for Metagross. Skarmory and Normals are hit harder by Return, no matter which Hidden Power you choose. You can put Sleep Talk over one of the other moves, but Facade is not boosted by Sleep, so you're better off not using them together, generally.

Name Item Nature

Endeavor

Liechi Berry / Starf Berry Jolly
Moveset EVs
~ Substitute
~ Endeavor
~ Baton Pass
~ Return / Quick Attack
4 HP / 252 Atk / 252 Spe

Substitute down to low HP, Endeavor the enemy, and then kill them with your attacking move. Return is better for general sweeping purposes, but Quick Attack works as a way to finish off Salac Pokémon and helps against Ninjask. Swellow is decent at causing switches if you bring it in on something like Heracross or Blissey, so you can often save a Substitute as they switch. Once you see what they have out, you can decide if you want to attack them or Baton Pass your Substitute to something that will survive their hit. If you get down to low health, and are ready to Endeavor, but know they will kill you next turn, you can always Baton Pass that Liechi out to some sweeper to soften up their team, and then bring out Swellow later for clean up. This is the advantage of its Speed—it doesn't need a Salac boost to be fast enough to Endeavor properly. You can just keep Swellow in the wings, threatening to Endeavor whatever late-game enemy is blocking a member of your team, or simply killing low HP enemies along the way. You don't need to Endeavor immediately after Substituting down low.

Other options for the item are Salac Berry or Petaya Berry, depending on your team, but Liechi is guaranteed to at least help Swellow (especially if you have Return). Starf is a real option, though, as no boost is useless when you are passing it. Seriously, what is your enemy going to do to a Choice Band Salamence when their counter takes 50% damage from it and can no longer OHKO with Ice Beam thanks to +2 Special Defense? Planning on trapping Heracross with Dugtrio after it kills something to Aerial Ace it? Too bad Heracross survives with +2 Defense and kills you back with Megahorn.

Other Options

Hidden Power Ghost can work to stop those Ghosts who think they can wall you. Sleep Talk makes Swellow a nice Sleep absorber, though most Sleepers can hit it quite hard. Hitting them with Guts attacks while Sleeping makes for a great surprise, though.

EVs

4 HP / 252 Attack / 252 Speed with Jolly nature. Adamant can be used, but that puts you slower than things like Timid Raikou, which is very important to beat. With Adamant, Jolly Tyranitar can outspeed you with Dragon Dance, but with Jolly, you can switch in on the Dragon Dance and surprise it with a OHKO Hidden Power Fighting (Tyranitar does have a small chance of survival, though, so just hit it as it comes in on one of your Pokémon with whatever).

Opinion

You need to get this thing statused as soon as possible for the Choice Band set, or it's just a weaker Dodrio with a lot more speed. Works as a great anti-stall Pokémon in ubers, however, as with Jolly, it's faster than everything but Deoxys-A (who will switch out nearly all the time for fear of Quick Attack, and can't switch in on anything) and weather abusers like Exeggutor (Mewtwo is almost never +Speed). Toxic is everywhere in ubers, so Choice Band Facade sweeps teams (it 2HKOs Lugia, Deoxys-D, and Groudon, and OHKOs everything else not resistant, really). Even Metagross can get 2HKOed by this thing with a couple of Spikes down.

Counters

Skarmory and Forretress can come in, take virtually no damage from its moves, set up Spikes, Rest off the damage, and then kill it with pretty much anything. Even if Forretress' only attacks are Earthquake and Rapid Spin, it can often stall out the Choice Band set of PP while slowly whittling it down with Rapid Spin, if you really want to be cruel to Swellow. Steelix, Metagross, Rhydon, Golem, and Aerodactyl take virtually no damage from Swellow, even if it uses Hidden Power Ground / Fighting on them, and will scare it off with Rock Slide. Ghosts like Gengar and Dusclops can switch into its STAB Normal attacks and kill it, but if Dusclops' only attack is Shadow Ball or Night Shade, it won't do anything back, because the last thing you want to do is Burn a Swellow.

Swellow also can't really take a hit well, so bear that in mind it's not as hard to counter as it looks. Note that Swellow is in the BL tier, and is thus banned from UU tournaments in Smogon, unlike many sites that allow 1-2 BLs per UU team.