Gengar (M) @ Life orb / Black Sludge / Wide Lens
Role: Rain Sweeper
EVs: 64 HP / 128 SAtk / 64 SDef / 252 Spd or 252 Sp Atk / 252 Spd / 4 Hp
Timid Nature (+Spd, -Atk) or Modest Nature (+SAtk, - Atk )
- Hidden Power [Water] or Giga drain ( Black Sludge )
- Focus Blast ( If you sub Giga Drain in, consider HP fighting! )
Well, here's a naturally beasty ghost, joining the rain squad.
While he has to compete with Jellicent, who has boosted STAB ( Much needed ) he gets Thunder instead of Thunderbolt and a new HP option, that packs a punch.
Hex is my choice of STAB, just because I love the move and it's general idea ( Thunder has a 30% chance to paralyze, so I can always take chances ) but Shadow Ball is a completely fair replacement if you don't like taking those kinds of chances.
HP Water is coverage, while you can sub this for something like Giga drain to break up Swamperts, Quagsires, and the devistating Gastrodon, murderer of all rain.
So that's always an option, it makes him a definite anti-water if you take onto that. You can also consider Black Sludge as an item if you pair him up with Giga Drain.
Focus Blast is your last move slot, Fighting + Ghost coverage is known for being pretty beastly, and that high powered coverage just gets me. I've experimented with Wide Lens with Thunder and Focus Blast, considering that some people can stop my weather, and that screws Gengar all up accuracy wise, but I preffer Life orb. Wide Lens still can work, if you aren't good @ weather wars :D While if you sub in Giga Drain for HP Water, HP Fighting can be fufilling.