The Iron Knuckle is my favorite enemy. They look awesome, they're pretty hard, and there aren't that many of them. Nothing much left to say about them.
I like the moblins. Not too sure why, but I just love them. I think it's because (long before I played Zelda) I'd watch my cousin play and kill moblins, and they just seemed to fascinate me.
I really like the wolfos because of the amount of fun I had fighing them, and I also liked their somewhat creepy but really cool apperence. My favorite enemy, though, was dead hand minibosses at the bottom of the well. I really love how they seem to stand out from all the other enemies in terms of being disturbing. The redeads just couldn't quite match them in this respect. I also found it quite challenging to try to not get stuck in the arms coming out of the floor. I think that it should be on this list.
Out of these, I'd have to say Stalfos. They're these pile of bones that can fight like a swordsman! And they can actually be challenging at times. Overall, though, the Darknuts. (You left them out. And, no, they're not the same as Iron Knuckles.)
I voted for redeads/gibdos, not necessarily because they're my favorite, but more because they seem to stand out to me as interesting enemies. I was seriously terrified of them when I was younger (eek...), part of that being that I really didn't know how to beat them. They leave you completely helpless, the worst position you could be in against any adversary.