I have quite a list, i enjoyed many of the enemies.
Ubsitvo, love the resemblance to the Super chainsaw maniac from the waterworld in RE4 mercenaries(same moveset when he swings his arm rapidly) I believe he was really well done and i was surprised by his presence.
Napad for some reason reminded me of hunters, except they were more of a tank and delivered much more of a payload when they strike you, minus the possible one hit kill that Hunters could do.
Brzak, first thing that popped to mind was Neptune! The amount of intensity that arose near the end had me on the edge of my seat and i really enjoyed his encounter.
Debroah, Considering i didn't look at any spoilers prior to the games release, this was a big shock for me, but then again it was something that could easily be predicted.
Ustanak, Oh Nemesis, your cousin is as persistent and stubborn and pain in the a#$ as you were that's for sure, ain't nothing like feeling like you're being chased across the world by something intended to murder you, the good old days of RE3...
Haos, A friend of mine i was playing Chris's campaign with said take a look at his face when he pops out of the Chrysalid, "Ramon Salazar" How does Haos's facial structure look like Salazar in any way? Or it was probably the way he hatched, who knows. The sequence where you climb the room was a bit tedious, but i enjoyed the rest.
Derek C. Simmons. Of course he had that William Birkin feel to him, except that he was in control for the most part while the virus spread through his body, the T-rex form was my favorite above all, but his final form... Oh, my, lord, epic as heck but... *rage*
But there's one that had my hopes up through the roof, but somewhat let me down.
Carla Radames. Her mutation was brilliant, her physical being taking over the aircraft hangar was brilliant, gave you the feeling that death was all around you because really, Carla was all around you, just the final part where you are able to kill her was... It could have been so, SO much more, it had that horror feel that i had been craving, not saying the rest of the game didn't have the horror feel, but there could have been so much more thrown into her segment.
Well, that's my two cents, there's more but that's just off the top of my head, and no i'm not dead, Diablo 3 suddenly got good and i'm hooked again... Somebody help me!!!