First non-D&D rpg you played.
The first non-D&D rpg I played was a home brew take on the World of Darkness. It used dots, d10's, all the class WoD things. The game was called Oddities and my friend's GM friend, Brock ran it. It had many of the World of Darkness aspects, like vamps and the Technocracy (who were basically the agents from Matrix). You could theoretically make whatever you wanted. The catch was the more power you had, the more you were hunted by the Technocracy.
The game was a lot of fun. My first character, well I don't remember his name but his power was a "holy ray." He could basically expel positive energy from a ring. We kept making jokes about him talking into his ring and saying "Get him Ray." That particular campaign lasted maybe two sessions, but we played many oddities games afterwards. We adapted the rules to play various anime games, notably Gundam and Dragonball Z.