Helseth is the #1 guy I hate in TES series. He tried to get me killed and made it IMPOSSIBLE for me to join the Dark Brotherhood in Morrowind (My favorite Guild!) I killed him like the filthy pig-king he was... Then took his epic ring!

My favorites (Can't Pick so will list faves from each game and faves that are in multi-games):
Daggerfall/Morrowind/Oblivion/Skyrim - Sheogorath.

Morrowind/Oblivion/Skyrim - M'aiq the Liar.

Oblivion/Skyrim - Lucien Lachance.

Skyrim - Paarthurnax.

Oblivion - Martin.

Morrowind - Sotha or Vivec. You didn't met Sotha before his death but he had a fun quote in a book. "If you're going to be stupid, at least be funny."

Daggerfall - The Underking. He was the one I give that stone thingy-ma-bob to due to him being the only one that wants to use it for a good reason.. Seriously, being cursed to live forever is not a happy thing and he wanted to use it to only bring his death.. I felt bad for him.

Martin Septim I guess, and for some reason the Khajiit Healer in Leyawiin Tsavi, probably because she reminded me of a Female version of my character, she was cool though

Paarth is awesome. His selfishness is fascinating.

Radac Stungnthumz. First dwemer i met and he was pretty hilarious too. Yagrum Bagarn comes second altough he just creeps me out. (i <3 dwemer.)

Vivec or Divyath Fyr. I also have a great deal of pity and respect for Martin.

The dark elf across the cell from you in the beginning of Oblivion, because he made me try out every race just to see how he insulted me.

http://www.youtube.com/watch?v=3XG3mUM7K0k

I may be a bit strange, but I think Martin Septim might be my favorite.

absolute tie between M'aiq the Liar, Aela the Huntress and Sheogorath. all three are beyond epicness

Divayth Fyr, Vivec, Barenziah