Gengar

Levitate
This Pokémon is immune to Ground-type moves.
Type Tier
Ghost / Poison OU
Statistics
Min- Min Max Max+
HP
60
- 261 324 -
Atk
65
149 166 229 251
Def
60
140 156 219 240
SpA
130
266 296 359 394
SpD
75
167 186 249 273
Spe
110
230 256 319 350
Name Item Nature

Status

Leftovers Mild / Rash
Moveset EVs
~ Thunderbolt
~ Ice Punch
~ Hypnosis / Will-O-Wisp
~ Destiny Bond / Explosion / Focus Punch
156 Atk / 168 SpA / 184 Spe

Bring it in on one of its many immunities and resistances, and start predicting and kicking ass. Thunderbolt / Ice Punch is about as good as the often hailed Boltbeam combination, and Gengar can hurt the standards that wall it (Regice, Snorlax, Blissey) pretty well. Hypnosis is a free Sleep on a counter and Will-O-Wisp messes up physical attackers which come in pretty often. Metagross is a good example.

You can change this set around as much as you want. Generally Thunderbolt is kept, any combination of the moves listed works. Particularly funny combinations are: Hypnosis + Will-o-Wisp, which should mess up two Pokémon pretty well, and Destiny Bond / Focus Punch, where you can pretty much force your opponent to kill you or eat repeated Focus Punches (if they let you lose focus and kill you, they go down with Destiny Bond). Ice Punch can be replaced by Will-O-Wisp pretty easily as most things you would Ice Punch (Salamence, for example) don't like being Burned either.

Name Item Nature

Mc(Ice)Gar

Leftovers Mild / Rash
Moveset EVs
~ Substitute
~ Focus Punch
~ Ice Punch
~ Thunderbolt
156 Atk / 168 SpA / 184 Spe

Substitute and Focus Punch is a combo commonly used in Advanced, and this set is no exception. This set suffers problems from Swampert and Blissey that use Ice Beam, so a second strategy of removing them is highly recommended. Spikes is also recommended since Gengar is a Ghost-type anyway and can easily block Rapid Spin.

With this set, Gengar can beat Blissey one on one most of the time. Seismic Toss doesn’t affect Gengar thanks to its Ghost-typing while Substitute blocks any attempt of status inflictions on it. Focus Punch not only harms Blissey, but also Snorlax and Tyranitar that may attempt to switch into Gengar. Ice Punch injures Zapdos and Claydol while Thunderbolt maims Skarmory and Gyarados.

The given EVs allow Gengar to 2HKO (48 - 56%) the standard Blissey most of the time with Focus Punch. 184 Speed EVs give Gengar 302 Speed, enough to outpace Adamant Salamence. The remaining EVs are poured into Gengar’s Special Attack stat to boost Ice Punch and Thunderbolt.

Name Item Nature

Mixed Sweeper

Leftovers / Liechi Berry Mild / Rash
Moveset EVs
~ Sludge Bomb
~ Ice Punch / Shadow Ball
~ Thunderbolt
~ Explosion / Focus Punch
156 Atk / 168 SpA / 184 Spe

Sludge Bomb does only about 30% to max HP / Defense Blissey, though after a few Sludge Bombs they're going to use Softboiled. That's when you Focus Punch it for the kill! Thunderbolt is for Skarmory and those Water Pokémon that are everywhere, Ice Punch for Salamence and Claydol. Use Explosion when you're at the end of your run and want to take something out. Sludge Bomb takes about half Celebi's HP and comes handy more often than Shadow Ball.

Name Item Nature

Choice Band

Choice Band Lonely / Naughty
Moveset EVs
~ Sludge Bomb
~ Focus Punch
~ Thunderbolt / Fire Punch / Shadow Ball
~ Explosion
252 Atk / 4 SpA / 252 Spe

With max Attack, Choice Band, and Adamant nature it gets 372 Attack. Focus Punch hurts a lot of stuff and is probably the move you will be using the most. With three immunities, it's really easy to switch in. You could throw in Thunderbolt for Skarmory if you wish.

Name Item Nature

Perish Trapper

Leftovers Jolly
Moveset EVs
~ Mean Look
~ Perish Song
~ Substitute / Taunt
~ Destiny Bond / Hypnosis / Protect / Substitute
252 HP / 116 Def / 140 SpD

A great surprising set for those people who send in their Ice Beam Swampert / Blissey to deal with Gengar. Mean Look, Perish Song away. If people get the gist of this and send Skarmory, Taunt it to prevent Whirlwind / Roar. Hypnosis can help you pull this set off; however, both the accuracy and Gengar's Defense are below average, so it's risky. Destiny Bond can assure you always kill something slower. Substitute and Protect stall for turns.

Other Options

It can Giga Drain if you are really afraid of Swampert. Spite and Snatch are fun as well. Special mention goes to Torment, as most Pokémon only have 1 move that can hit Gengar. Torment, and Protect / Substitute when they try to attack you and feel free to attack while they can't do a thing. Swampert, Blissey, Metagross, Snorlax are examples of this. Fire Punch is an option to take out Forretress and do some damage to Steelix, and other Pokémon that aren't really injured by Thunderbolt. Psychic hits Heracross and enemy Gengar hard, but is worthless on Tyranitar / Metagross switches.

EVs

You can replace any of the natures with a +Speed nature. You'll want at least 300 or 334 Speed, depending on what nature you are using. The rest should go in Attack and Special Attack. Mc(Ice)Gar can use 252 SpD EVs to prevent Blissey from breaking Gengar's Substitute with Ice Beam.

Opinion

The most unpredictable Pokémon in OU, no questions asked. It has an awesome movepool and the stats to use it. 3 immunities and 4x resistance to Bug and Poison make it easy to switch in. Gengar is probably the best Ghost Pokémon in the game.

Counters

Dusclops comes in rather easily on anything but Choice Banded Shadow Balls and can Shadow Ball back, which will hurt. It will need to restore HP with Pain Split or Rest soon though. The Rest + Sleep Talk variant of Dusclops counters even Hypnosis Gengar. Sableye with a lot Special Defense and HP EVs can come in nearly infinitely on most Gengar, threaten with Shadow Ball, and Recover to shrug off hits.

Swampert works if Gengar doesn't have Giga Drain, but doesn't like the Perish Trapper or Will-O-Wisp surprises. Claydol is also immune to Thunderbolt, and doesn't take too much from Ice Punch, so it will beat Gengar as long as it has Psychic (or even Shadow Ball).

Raikou can Substitute + Calm Mind up against it and Jolteon can use Volt Absorb to repeatedly come in, but don't let them eat physical hits. Celebi doesn't take more than 50% from anything Gengar throws at it, with the exception of Choice Banded Sludge Bomb or Shadow Ball. It can Recover off hits and OHKO Gengar with Psychic, but watch out for critical hit Ice Punch or Fire Punch, which can happen if Celebi repeatedly Recovers. Calm Minding up against Gengar will slowly weaken its hits. Jirachi is an good overall counter; even Fire Punch doesn't take it out within 2 hits. Needs Wish and kind of needs Protect to keep up with that, but for the rest it does very well with Psychic.

Blissey can paralyze Gengar with Thunder Wave, or damage it with Ice Beam. Keep her out of Focus Punches and Explosions, as well as the Choice Band set. As long as Snorlax has Shadow Ball, it will beat Gengar. Even Hidden Power Steel or Fire Blast will be enough to stop it.

Metagross OHKOs with Meteor Mash, Shadow Ball or Psychic and, with some Special Attack EVs, Pursuit if Gengar decides to switch out. You will find it Will-O-Wisped or Hypnotized more often than not, so Rest + Sleep Talk Metagross is the best option for this. Tyranitar can Pursuit as well, but generally Sand Stream, Crunch or that STAB Rock Slide is enough to deter Gengar. Keep it out of Focus Punches as well. Houndoom is nearly 2HKOed by Thunderbolt and OHKOed by Focus Punch, but can OHKO with Crunch, or Pursuit if Gengar decides to switch.