Mine has the ability Speed Boost. It knows:
Bug Buzz: Good power, high accuracy, STAB, chance to lower Sp. Def.
Air Slash: Decent power, decent accuracy, STAB, good chance to cause flinching which works great with Speed Boost.
Protect: Lets Yanmega get a speed boost.
Hypnosis: Puts the foe to Sleep. When and if they wake up (Yanmega could easily KO them) they'll wake up to a very fast Yanmega.