Star Wars D6 RPG (1st edition) with the Star Wars Sourcebook, Imperial Sourcebook, Rebel Sourcebook, Rules Companion and Gamesmaster's Screen.
WFRP (1st edition) with Warhammer Companion and Gamesmaster's Screen.
Prime Directive (Task Force Games) but I play this with the D6 system.
Buck Rogers XXVc with Belters Supplement and Comic Module Issue 1.
Dragon Warriors with the Bestiary and the Sleeping Gods and The Elven Crystals adventures.
And I suppose I can include in that my Fighting Fantasy and Advanced Fighting Fantasy books, and - believe it or not - 'Darksword Adventures' by Weis and Hickman.
That was quite a cull. I'll see if I can remember what it was I owned and post that, too. I can see myself getting quite teary if I do that.