Hmm... A bulky gengar? It seems like something like Jellicent or Cofagrigus would be more effective, and you're wasting gengar's andvantages of speed and wallbreaking power. But hey, if it works for you...
Celebi@Choice Band
Natural Cure, Adamant nature
4 HP, 252 Atk, 252 Spe
-Seed Bomb
-U-Turn
-Sucker Punch/Trick
-Zen Headbutt/Trick
Celebi's actually kinda decent with a band. Sure, his coverage sucks, but it's amazing for smashing bulky waters in the face, as none of them like to take seed bombs and scald does nothing-even burn can be switched out with natural cure- and dealing with common celebi checks and counters- blissey, roserade, and hydreigon, for example, all take massive damage from u-turn, not to mention it fucks over lati@s. Sucker punch can revenge kill a lot of things that don't expect it (and ask yourself: did you even know celebi leaned sucker punch?) and hits decently hard, nearly KOing latios, and zen headbutt crushes fighting and poison types like machamp, conkeldurr, toxicroak, and tentacruel. Sure, it's a bit gimmicky, can't hit steel types, and doesn't hit as hard as a powerhouse like scizor, but it's general bulk and utility is nice and it's really fun to use as it generally takes easy KOs and confuses opponents. You can run a bulkier spread, a special coverage move, or trick to mess with walls, but personally I think vanilla CB works fine.