For me...
FAVOURITE:
5. Marcus Fenix (badass, great character in the third GoW game)
4. Spartan Thorne (Seriously, watch Spartan Ops Episode 8, he's tank, and a good character)
3. Gordon Freeman (purely awesome, and his voice actor's the best in the business)
2. Dominic Santiago (Don't want to spoil it, but Act 3, Chapter 5... D;)
1. Master Chief (not so much in the other games, but in 4, he really came into his own and had a FAR better character IMO)
DESPISED:
5. Damon Baird (I still like him, but GOD he gets annoying...)
4. Annoying Fan (need I say more?)
3. The Didact (HALO 4 SPOILERS: He killed Cortana and I didn't think he was a great villain. He just made no sense. Read the books and such and you will see)
2. Whiterun Guard: (Oh, you saved the world from its inevitable doom? NO LOITERING)
1. Admiral Del Rio: The biggest dike out there. For no reason whatsoever he's a total nob to Chief and Cortana. I don't know what I disliked more, the over-the-top stereotypical good-guy-is-bad or the disrespect he shows for them. They only saved the galaxy...