Duke Nukem 3D with the attrition mod. I pretty much grew up on that game and with that mod I've yet to run out of content to play. Also the Need for Speed series before it got into the whole illegal street racing thing, though I liked Most Wanted and Carbon.
And Minecraft. The only game I can play with my friends on PC(integrated graphics) and my younger cousins(parents follow the rating system by the book, cousins just turned 10, unrated games FTW)
I used to be proud to be an audiophile, but when you go from "isn't $50 a bit much for a headphone" to "cool, only a few hundred" and you start selling off parts of your PC to get your next fix... oh well. It's still cheaper than being a car guy.