Zant was... indescribable.
All of the other bosses were totally serious. Some people may like that, but Zant... well, let's just say I lost a few times due to the Wii remote falling out of my hands because I was laughing so hard.
His strange sounds, his erratic hand motions; everything about him is just insane. And that's exactly what I like about him. Another thing was the twist of plot. We all were expecting some amazing new villain, and then, boom-- he's just a pawn. Plot twists are my love.
Another thing was the fact that he brought you back to places you fought before-- I thought that was an ingenious idea. I thought I was never gonna see those places again! The battles were actually fairly easy; but, again, Zant made them all the more interesting.
I swear, I think Nintendo designed him to be so funny that you couldn't beat the boos because you were cracking up laughing. I applaud them for succeeding xD