Playing 10-15 year old DOS & Windows games, chiefly shareware & abandonware.
So far, I've been having fun with D/Generation (which my sophomore year roommate had), Dungeon Master (which I played for hours and hours on my Amiga 500 in college), Oregon Trail ("The river was too deep to ford. You lose 5 oxen and little Johnny."), Jill of the Jungle, Commander Keen 1, Commander Keen 4, Duke Nukem 1, Squarez, Jetpack, God of Thunder, Tyrian 2000, Hexxagon & Hexagon II, and more.
I'd play Scorched Earth for hours, but the game files I've found for download (the ones that don't require signing up for a "site membership", that is) don't play nice with modern CPUs--either they don't work at all, or the action is *way* too fast. (Though now that I've seen it, I may have to try the 3D version...)
Feudalism: Serf & Turf