[RiderSkyward]

I think OOO's has the best, both visually and musically. The swirling energy medals look cool and work as defence, and the jingles are damn catchy.

Second place would go to Fourze and his base states henshin, smoke and bright lights to protect and the awesomeness of the 3..2..1 build up. Oh and the whole reaching for the stars pose thing =]