Simple zombie, Eye of Cthulhu, lunatic cultist, golem, meteor head, fire imp, wywern, that one underground enemy I forgot the name of which looks a lot like a hercules beetle, emerald bunny(?), nymph, the guide (he is an enemy for letting zombies eat your brain), the merchant (for selling overpriced safes), arms dealer (for selling a weapon which you get the better version of before you get the money to buy it anyways), dungeon spirit and ??? from solar eclipse...
That ought'ta keep you busy for awhile!