Probably some of the best designed armor ever.

Aldmeri Dominion at first because in the beta they didn't seem to be as evil as they are in Skyrim. The beginning of some of the quests showed them to be quite honorable and different to what they morphed into later on. Plus Raz is hilarious, the starting area is great and I really want to see Summerset Isles, Valenwood and Elsweyr. I'll eventually try all of them though.

Daggerfall Covenant, there can be no other option.

If you join AD then you WILL get fleas. Its a true fact. Also, I heard that they aren't having the Khajiit spayed and we all know what kind of problems that can lead to...

If you join EP then you'll probably die of salmonella because everyone knows you can get salmonella from touching reptiles (especially unclean reptiles. Which all Argonians are. Once again, its a true fact).

So as you see there is only one option to join if you don't want to get really sick or die.

Unfortunately I have yet to run into an altmer that wasn't. Starting with the first one you meet in Seyda Neen.