I'm quite fond of Avira Personal. Works like a charm and isn't resource hungry in the least. Teh free version gives a pop-up ad to upgrade after every update though, but still works like a charm. Used the free version for a few months, fell in love with it and bought a year's subscription.
lol... Never heard of Puzzle Quest Galactic... I've finished World of Goo, but the OCDs are surprisingly irritating to achieve, Trine doesn't appeal to me and I can't afford Braid until end of the month...