As someone already said, human noble from city elf origin, Edgar Ross (I just couldn't put enough bullets in that asshole), Noober in Baldurs Gate (hardest thing is to resist killing him when you're playing good party), any NPC in LEGO games, main guy from SoF payback (game was awful), Niko Bellic cause leaping off buildings and crashing your car/flying through windshield is always fun (and the way he pronounces Bosnian/Croatian/Serbian words with ridiculous russian accent is insulting at least), Starkiller when controls feel unresponsive etc.
Hmmm, reading all this made me realize I should probably concentrate more on playing game than killing off main characters.