That's a hard one. I'm not a fan of the piercing swords in general, but their charge attacks are fun to use. Brandishes have a boring combo, and their charge attacks are so easy to use with such high payoff that they're not even interesting. Fire and freeze are more fun statuses to play around with than shock so I suppose Voltedge?
The jelly guns are also close contenders, but sometimes I enjoy manual rapid-fire.
Shards. Never Forget.