Alien Godola (ゴドラ星人 Godora Seijin)
Unceremonious death aside, the Alien Godola — in character and design — are pretty great. They spend most of the episode cackling madly and taunting every human they come across.
Bemlar (ベムラー Bemurā)
Bemlar may not be Ultraman's most exciting adversary, but, in the Ultra series history books, he is perhaps the most important one. Bemlar is the first giant monster to have the living snot beaten out of him by Japan's favourite Protector of Earth and Slaughterer of Mindless Monsters.
Alien Spell (スペル星人 Superu Seijin)
Alien Spell has a more interesting back story than any Ultra monster - I'm not talking about his narrative history, but the controversy his episode, "From a Planet with Love", generated back in the late 60s.