I actually LOVE the Iron Knuckles!! I wish there would have been more of them. They are really easy to defeat once you know how to defeat them. I would say floor or wallmasters. They are not that hard to defeat but especially the way they look. Creepy and intimidating
I go with the floormasters from Ocarina of Time. The thought of little hands climbing up your body to strangle you is pretty... disturbing to me. I always shrug at one point in Forest Temple when you have to fight some of those for a key. That validates the saying "spin attack is your best friend" in my eyes.
On the other side, Death Hand is pretty messed up. I'm torn between them.
Cuccos, simply for the fact that you can't kill them. I have my technique down perfectly for all the other enemies, so they don't really scare me anymore. But when I first played OoT when I was like 9 or so, Iron Knuckles for sure. I would use all my bombs and din's fire so I wouldn't have to even approach them. HA