Ghirahim is pretty cool. I was surprised by him actually because he looks unlike any other Zelda character I've seen. Very interesting for Nintendo to go with a character of that style. 

Fi is also really cool. Not sure how far you are in the game but after you beat the first temple she does this beautiful dance that looks like ice skating on the water. She's pretty neat. I think I might cosplay as her next year.

I'm not very far in Skyward Sword yet. I'm only in the second area on the surface.