Any game from Good ol Games (www.gog.com) is DRM free. And, you can download it as much as you want to any computer you want after your initial purchase. Every couple of weeks, they keep adding more and more games. Sure, it's older games, but hey, some of them are the best!
Duke Nukem 3D Atomic Edition! Groovy!!!
BTW, I haven't had any DRM screw up my system. That's not to say I like it, but if I feel the game is worth it, I'll get it. Of course, Assassin's Creed II will NEVER be purchased NOR played by me until they remove the constant online restriction. That is completely uncalled for. But, it looks like they're aren't going to quit using it any time soon.