Smeargle is a veteran of Baton Pass chains and the main reason why they are not easily countered by phazers. Even outside of a full chain, Smeargle can cause a loss right away because passing a Belly Drum and a Salac boost to, say, Medicham, will simply be "good game". Beware of Smeargle, despite its fragility.
As of March 2011, Ingrain is illegal on Smeargle in Smogon Tours, which makes some of its main sets obsolete.
This Smeargle is meant for us on full Baton Pass chains, and keeps the chain from being phazed. If your chain lacks Umbreon, Spider Web is very important as it also prevents Haze from destroying the team. It can be used over either Spore or Substitute, but Ingrain and Baton Pass are required moves.
These EVs guarantee Smeargle survives Zapdos's Thunderbolt, which is about the strongest unboosted special attack used in standard, so it'll survive attacks such as Starmie's Surf as well.
The ultimate instant Baton Pass setup; this Smeargle works marvels. Its execution is simple: send out Smeargle against a slow threat and use Substitute. If your opponent brings in a Pokemon that doesn't have phazing, hazing, or multi-hit moves, use Belly Drum; otherwise, use Spore. Set up and pass a Belly Drum boost as soon as possible, then proceed to sweep with Medicham, Aerodactyl, Cradily, or Gyarados. Medicham is the best if you can guarantee the pass as, at +6, it OHKOes every single Pokemon in OU. Cradily, however, has the benefit of being immune to phazing, making it easier to pass to. Aerodactyl and Gyarados are easier to switch in and can Taunt bulkier threats they can't OHKO.
This Smeargle does appreciate being paired with the likes of Exploud, Mr. Mime, Magneton, Octillery, or Cradily, but it is not required.
A dastardly surprise, this Smeargle is guaranteed one kill in a match if your opponent does not have a Ghost-type and doesn't know what you are pulling. Endure a hit from just about any Pokemon, put it to sleep with Spore, and unless facing a Sleep Talk user, use Endeavor. If the opponent stays in, attack it with your last move, and repeat the cycle. It's more likely that the foe switches, in which case feel free to use Endeavor on the switch-in too. Now, Smeargle will have put one opponent to sleep and left another one a sitting duck at 1 HP. Beware of Reversal and Flail though. Some opponents are so shocked by this that they make odd switches, and every switch to a new Pokemon means another Pokemon screwed by Endeavor.
Where this set really shines, however, is in 2v2 Stadium Mode. Lead with this guy and a Pokemon that knows the move Explosion or Selfdestruct—the higher Attack and Speed they have, the better. Use ExtremeSpeed in this mode of play: it helps against the likes of Rayquaza. As Smeargle's ally uses Explosion or Selfdestruct, Smeargle should Endure the hit. Next, send in a Pokemon that has Fake Out—Jynx is preferred, but Persian works as well. If one enemy is faster than your Fake Out user, Spore that one and target the other with Fake Out; otherwise, Spore the Pokemon less likely to be carrying a Lum Berry (as there is Item Clause, only one Lum Berry is allowed per team). Next turn, Endeavor the Pokemon that is awake, and finish it off with Jynx's Ice Beam. Repeat this strategy on every awake Pokemon, then finally finish off the sleeping Pokemon.
The last 4 EVs on this set have been omitted because they would be detrimental to this Smeargle's quality; it needs to be able to get to as low HP as possible after Endure for Endeavor to work well. The 0 HP IVs are there for the same reason.
Set this Smeargle to level 5, and pair it up with Sand Stream Tyranitar. It is nearly impossible to switch in, but if you manage to do so and there are no Ghost-types on the opposing side, it will screw up at least one opponent. Substitute or Spore when you can to buy a little more time, and Endeavor anything you can. Due to Smeargle's extremely low HP, all bar immune opponents will be put straight into Sand Stream's KO range. The last move finishes these foes off, and all others if sandstorm isn't up. While Dragon Rage does more damage, ExtremeSpeed stops Salac-boosted Pokemon at 1 HP from ruining this set; it'll be doing about 2 HP damage to most Pokemon. This set is extremely deadly, especially if your opponent doesn't wise up to the fact that it is level 5 and switches in its sleep absorber without realizing that everything is faster and powerful enough to KO it.
One of the easiest ways to switch this Smeargle in is by pairing it with a Pokemon with both a trapping and a sleeping move; Mean Look + Lovely Kiss Jynx, Block + Yawn Snorlax and Mean Look + Hypnosis Gengar are all good options. Smeargle essentially needs one turn to switch in and one to set up with Spore or Substitute. If you ever encounter something that cannot really touch him, such as a Pokemon with no attacking moves or only Ghost-type moves, use that to switch Smeargle in more than once.
Smeargle's EV spread and hold item will likely not matter. One thing to note, though, is not to give Smeargle HP EVs when running this set; this will reduce Endeavor's damage. In fact, you'll want to set its HP IV to 9 or less. This gives it 20 HP, which is the minimum possible. Defensive EVs, on the other hand, are helpful on this set because this Smeargle's HP is low enough that it can KO most anything with sandstorm damage, so it doesn't need to take any more damage than sandstorm will inflict. Meanwhile, the defensive EVs might help Smeargle, unlikely as it is, survive something.
OHKO moves are banned, but this is the next best thing to using Lock-On + Sheer Cold. Predict a switch, use Spider Web, Spore the switch-in, put up a Substitute, and start the countdown with Perish Song. Spam Substitute and Spore while waiting in case your opponent wakes up before fainting. This set has trouble with Sleep Talk users such as Heracross.
The EVs given maximize Smeargle's Speed, then boost its defenses.
After a Belly Drum boost, STAB ExtremeSpeed and Explosion both hurt. While not the most common set, it is still effective; to illustrate, a Belly Drum-boosted Explosion OHKOes Skarmory. Put the last four EVs into Defense rather than HP in order to Belly Drum twice.
Transform is, surprisingly enough, a somewhat viable strategy; it allows you to scout out your opponent's moveset, and even use their moves—Spikes, Aromatherapy, Toxic, Light Screen, to name a few—against them. Transform also automatically copies any stat boosts your opponent has, so feel free to Transform into a Snorlax with a bunch of Curse boosts and try to beat it. While Smeargle lacks Snorlax's extremely high HP, its other stats will likely be superior.
As sleep absorbers are usual switch-ins to Smeargle, it might not be wise to use Spore first. In fact, this Smeargle can check if the switch-in is a Sleep Talk user by using Transform. Any number of utility moves can be used in the last two slots. Aside from the listed moves, other options include ExtremeSpeed to finish off Salac-boosted Pokemon, Whirlwind to counter Ninjask, as well as Spikes, Rapid Spin, and Aromatherapy. Finally, Reflect and Light Screen give Smeargle an edge after it uses Transform.
Smeargle is one of the two Pokemon in the game that can Baton Pass Tail Glow. If you pull that off and pass a boost to a powerful and fast special sweeper, such as Raikou or Zapdos, you can give your opponent a hard time. Other than that, while Smeargle has the movepool to perform just about anything in the game, the more useful options have already been mentioned, and Smeargle doesn't have the stats to pull off anything else.
Checks and Counters
Ghost-types block the Endeavor set. Quick Attack users and Ninjask hurt Smeargle a lot as long as they avoid a Belly Drum-boosted ExtremeSpeed. Phazers, Skarmory, Suicune, and Steelix in particular, scare all Smeargle, while Weezing can Haze away its boosts. As Smeargle will fall to just about any attack, sleep absorbers easily end it. Banette and Primeape are immune to Spore thanks to their abilities; Sleep Talk users work similarly as well.