Gengar is one of the fastest Mons(350 normal, 394 Mega) in OU, putting aside stat boosts and Alakazam(372 Normal, 438 Mega).... I'm pretty sure Shadow Tag stops working when you switch out as well, but I understand the idea.
Gengar-Mega @ Gengarite
Ability: Shadow Tag
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Hex/Shadow Ball
- Will-o-Wisp/Giga Drain
- Substitute
- Dark Pulse
Because of Gengar's awesome SpA, it doesn't need stat boosts, so it is a great pivot Mon. If there is a predictable Earthquake, Pivot to Gliscor for free heal turn. But I like this set for Gliscor:
Gliscor @ Toxic Orb
Ability: Poison Heal
EVs: 252 Spe / 252 Atk / 4 Def
Jolly Nature
- Roost
- Earthquake
- Fling
- Acrobatics
What's so great about Fling is that you can Toxic a potential Wall, as well as boosting Acrobatics.
Sigh, Celebi and Primarina... They are too weak. There are stronger water types, a.e. Gyarados, Mega Swampert, Pelipper is a setup Mon that you wanted for Celebi, Rotom-Wash(Gets Electric coverage), Greninja is OP, Toxipex is annoying, Keldeo, and Tapu Fini is sitting in the corner.
Gyarados @ Focus Sash
Ability: Moxie
EVs: 252 Atk / 252 Spe / 4 SpD
Jolly Nature
- Dragon Dance
- Waterfall
- Earthquake
- Ice Fang
This is your average Gyarados-Moxie sweeper. I use this a lot. :)
Weavile is wonderful, a nice offencive Ice type, but Weavile is an Ice cannon(lol puns). There are better ones: Mamoswine for a slow-bulky sweeper, Rotom-Freeze, the Kyurem's, and Cloyster.
Cloyster @ White Herb
Ability: Skill Link
EVs: 252 Spe / 252 Atk / 4 SpD
Jolly Nature
- Shell Smash
- Icicle Spear
- Rock Blast
- Rapid Spin
Cloyster is AMAZING, but it isn't reusable. Mamoswine has Priority and Kyurem is also Dragon.
:)