Quoted By:
1. Kangaskhan: Being both a superstar revenge killer and setup sweeper in one are huge boons. The only really hard choice in the moveset is deciding between crunch and suckerpunch.
2. Gengar: Gengar is and always will be one of the best pokemon in the game, and having the *option to be mega is just another asset. From perish trapping to just plain sweeping, Gengar can be a real asshole to deal with.
3. Absol: A stellar anti-lead; given an opportunity to swords dance freely out of the gate against the myriad of rock setters and followup with Sucker Punch creates a damned-if-they-do-damned-if-they-don't situation.
4. Pinsir: Whether it's a Moxie setup sweep or Mold Breaker Sneaky Pebbles lead, giving Pinsir a mega stone even with other megas on the team is a definitely viable option. STAB flying Quick Attack and Return are terrifying attacks, especially after a Moxie boost.
5. Alakazam: Falls in the same boat as Gengar. Having access to STAB psychic as well as Focus Miss and Shadowball on top of that insane speed makes for a terrifying sweeper.
6. Mawile
7. Venusaur
8. EdgyZard
9. Gyrados
10. Blastoise
Bottom three are easily Blaziken, Ampharos, and Gardevoir.