This is the first time I've done this, so let me know if I'm doing something wrong :P
[Overview]
<p>Looking at Cofagrigus, one might wonder why it isn't more popular as a Trick Room user. It has low Speed, amazing defenses, and fewer weaknesses than other Trick Room users, such as Cresselia, Reuniclus, and Jellicent. However, in the VGC 2012 metagame, Cofagrigus is overshadowed by Dusknoir and Dusclops, two similar Pokemon that possess both higher defenses and superior movepools. Furthermore, many players prefer using Chandelure or Jellicent to set up Trick Room, as they can sweep more effectively with their dual STAB moves. In truth, the only reason to use Cofagrigus over its competitors would be its unique ability, Mummy, which can cripple the likes of Scizor, Conkeldurr, and Heracross, who rely on their abilities to do anything of note.</p>
[SET]
name: Trick Room
move 1: Trick Room
move 2: Will-O-Wisp
move 3: Shadow Ball
move 4: Protect / Hidden Power Fighting
item: Mental Herb / Lum Berry
nature: Sassy
evs: 252 HP / 4 Def / 252 SpD
ivs: 0 Spe
[SET COMMENTS]
<p>Its pure Ghost typing gives Cofagrigus an immunity to Fake Out. This, combined with Cofagrigus's immense bulk, almost guarantees that it will be able to set up Trick Room on turn one. Will-O-Wisp takes care of physical attackers that would normally pose a threat to Cofagrigus, most notably Tyranitar. Shadow Ball is Cofagrigus's best attacking move, and does a decent amount of damage to Pokemon such as Latios and Cresselia. Protect can come in handy to avoid an obvious super effective attack while Cofagrigus's ally attacks or sets up. On the other hand, Hidden Power Fighting allows Cofagrigus to dent the Dark- and Steel-type Pokemon that give it trouble.</p>
[ADDITIONAL COMMENTS]
<p>A Sassy nature and maximum Special Defense EVs nearly even out Cofagrigus's defenses, allowing it to survive strong super effective attacks, such as Shadow Balls from Chandelure and Gengar. As Cofagrigus's only real strength is setting up Trick Room, any item that makes this easier is a viable option. Mental Herb is the best item for Cofagrigus, as it is an obvious target for Taunt. However, Spore and Sleep Powder also hamper its ability to set up Trick Room, making Lum Berry a viable option if you are afraid of Amoonguss, Breloom, or Venusaur ruining Cofagrigus's day. A Kasib or a Colbur Berry can be used to weaken Ghost- or Dark-type attacks, respectively, such as Choice Specs boosted attacks from Chandelure or Hydreigon. A Sitrus Berry can also help Cofagrigus stick around for longer, especially if it has Fake Out support to stop incapacitating moves, such as Taunt and Spore. Finally, Hidden Power Fire and Ice are both good options to use in place of Hidden Power Fighting, depending on the needs of your team.</p>
<p>Pokemon with Fake Out and the ability to hit Ghost-, Dark-, Normal-, and Steel-types super effectively, such as Scrafty and Hitmontop, are ideal partners to Cofagrigus. Follow Me and Rage Powder users can also aid Cofagrigus in setting up Trick Room by redirecting super effective attacks away from it. Lastly, Amoonguss is a great partner, as it has low Speed to work well in Trick Room, as well as the ability to reliably put opponents to sleep with Spore.</p>
[Other Options]
<p>Cofagrigus can run a more offensive Trick Room set with Calm Mind or Nasty Plot to boost its Special Attack, and with Hidden Power Fighting over Protect. Unfortunately, Cofagrigus's shallow movepool, along with its lack of secondary STAB, makes this option very unattractive, especially in such a fast-paced metagame. When Trick Room is in play, Cofagrigus can effectively use Disable to lock an opponent out of an attack; this can potentially remove a huge threat to your team or force Choice-locked Pokemon to Struggle or switch out. Cofagrigus has access to Destiny Bond and Memento, but those moves are better left to faster, frailer Pokemon that can make better use of their effects. Toxic is an option to cripple bulkier Pokemon such as Suicune or Blissey, but Will-O-Wisp is the more useful support move as it cripples physical attackers such as Tyranitar, who give Cofagrigus trouble. Finally, although Cofagrigus is bulky enough to run a ChestoRest set, this is often best left to other Pokemon as Cofagrigus's sole purpose is to set up Trick Room.</p>
[Checks and Counters]
<p>Even if Cofagrigus runs Hidden Power Fighting, Tyranitar is a serious threat as it can can OHKO Cofagrigus with a Dark Gem- or Choice Band-boosted Crunch. However, Tyranitar should be wary of Will-O-Wisp, which will leave it pretty much useless. Chandelure and Gengar can OHKO Cofagrigus with a Ghost Gem or Choice Specs attack, and can also use Imprison to prevent the use of Shadow Ball and Trick Room. Hydreigon can hit Cofagrigus hard with a Life Orb or Dark Gem Dark Pulse while taking little damage from Shadow Ball. Alternatively, bulky variants of Hydreigon can set up Substitute to block Will-O-Wisp, and then wreak havoc on your team. Houndoom, while very uncommon in the VGC 2012 metagame, completely walls all Cofagrigus that lack Hidden Power Fighting. Houndoom can also nab a Flash Fire boost from Will-O-Wisp and hit Cofagrigus hard with STAB Dark Pulse or Sucker Punch. In general, as Fire-type Pokemon are immune to Will-O-Wisp, any physical Fire-type sweeper, such as Infernape, Arcanine, or Darmanitan can potentially cause Cofagrigus trouble. Moreover, while Mental Herb can allow Cofagrigus to evade Taunt once and set up Trick Room, the opponent can Taunt a second time to block Will-O-Wisp and leave Cofagrigus helpless.</p>