I remember getting a Core War emulator running on my IBM PC/XT back in the day, but I was way too young (I think about 12) or perhaps just too uncommitted to really learn how to build my own warriors or truly understand the programming language used. But the idea of programming games has always appealed to me - another one I played around with for a bit was CRobots. I never seemed to manage to find something that had a really active community.