I came in this thread expecting it to be a thread about Rareware games, and I was all ready to list and brag about the dozens of games I own or once owned by them.
But if we're speaking actual "rare" games; up until recently I owned a hard copy of Bubble Bobble 2, which is apparently very hard to come by, and actually sold it on amazon for 90 bucks. Was quite a fun game, but not 90 bucks fun.