I can't pick just one. I'll list a few:
-Dream Eater: Just the idea of eating something's dream and stealing its health is awesome.
-Hi Jump Kick: WATAAAAAH!! Any questions?
-Flash Cannon: I dunno, I just really like this one.
-Thunder: The classic, all powerful electric move.
-Flare Blitz: Step 1, light yourself on fire. Step 2, throw yourself at enemy. Step 3, ??? Step 4, PROFIT!