Does PC count?
Because I almost feel guilty for the amount of fun I'm having with games that I barely even payed for. I've played almost 40 hours of The Witcher since getting my PC a month ago, and it'll probably go down as one of my all-time fave RPG's and I only paid $5 for it. $5 freakin dollars, that's 1/6 of what I paid for the mega turd Fable 3 just last Fall. It really has shattered my perception of videogames and value. This also goes for STALKER: Shadows of Chernobyl which was like $2.50 and Mafia II @ $7.50.
On the console side, there are much less instances of this since I was always a day-one whore for the stuff I was really interested in, but a lot of XBLA/PSN games come to mind. I've probably played like 15 hours of Joe Danger and I only paid $7.50 for it, what an awesome fuckin game too. Same goes for Peggle, which is so good that it's priceless, I would pay millions and millions for it.
This kind of stuff makes me feel like an idiot for spending $60 on so many games that did nothing for me.