I don't have a favorite. I can never decide jsut one. :shrug:
By "worst", I'm assuming you mean "least favorite"?
I really, really don't like orcs, all the orc NPCs are rude and all of them seem to be warrior brutes. I will never play as one, and I suppose that suits my playing style, since I prefer stealth and magic to combat.
...this. It's not so much that orcs are my least favorite, it's more the way they're portrayed in TES. I grew up playing D&D with the orc who lived in the forest, in an abandoned shelter or a cave along with goblins, kobolds, and such. Orcs are supposed to be brute, offensive beings, they're not supposed to run bookstores and wear finely-tailored clothing. Granted, I do have a laugh at some of the things orcs say in Oblivion, but I'd rather they be in their traditional place: in effect, always at the end of my blade or lightning bolt. I can't stand seeing them in towns, being mildly offensive at best.
Back in my D&D days, if somebody decided to play an orc, they were often shunned and/or tested by the rest of the party, because an orc could not be trusted. I think this friend of mine did play an orc for awhile who finally did become an ally to the party, but you have to understand that now this orc would have been seen as "civilized" whenever he encountered other LOTR style-orcs. Therefore, he always ran negatives against such creatures.
the same goes for lizardpeople as well. I'd rather see them in forests and swamps ONLY, bla bla bla...