I like the Argonians and Khajiit; they have the most interesting NPCs in my opinion. Well, except Sheogorath from SI, but Daedric Princes aren't playable without addons.
I like Argonians the most, though. I like reptile races, they can breathe underwater, they're immune to Poison and highly resistant to Diseases, their skill bonuses are nice (at least I think they are), and there's just something really appealing about one of the least-respected races in Tamriel becoming the champion of Cyrodiil.
Trenchant Informant said:
and the last are badass wizard lords that live in giant mushrooms
I like House Telvanni's rules.
Stole something from another Telvanni? Make it out alive and you deserve to have it.
Get into an argument that turns violent? The winner (read: survivor) is the one who's right.