Ok, my turn for this meme. The rules for the uninitiated: Don't take too long to think about it. Fifteen games you've played that will always stick with you. List the first 15 you can recall in no more than 15 minutes.
In no particular order apart from how they popped into my head.
Dungeons & Dragons (AD&D through 3.5)
Castles & Crusades (was tempted to include this above, but kept it separate due to the SIEGE mechanic)
The Classic Dungeon
Magic: The Gathering
Call of Cthulhu
Gamma World (4th edition of GW, not the current one based on D&D 4e which I have not played)
Ambush Alley (made me realize there is such a thing as a rules-light war game)
Nite Life (and old RPG with vampires and werewolves)
Battle Masters (the old miniatures board game)