Train
Is that all you got?!
I have to say that my favorite enemies are the random ones (thieves, assassins, roaming bandits, Thalmor, etc). Mostly because they make the world seem more real. I, of course, like fighting dragons, but I'd think that would be a given. I hate trolls at low levels, but like beating them down at higher levels when I can. Overall, I hate magic users the most, at any level, they seem way overpowered.