Off the top o' my noggin:
My 1st Edition books: DMG (two versions; one with the efreet, the other with the green robed wizard), PHB (the thieves stealing the eye-gems from the statue), MMI,MMII, Fiend Folio, Manual of the Planes, Deities and Demigods (w/out Elric and Cthulu

), Wilderness Survival Guide, Dungeoneers Survival Guide, Greyhawk Adventures, Unearthed Arcana, Oriental Adventures, 1E DMG Screen (w/the aforementioned green robed wizard on the front)
FRCS (2E and 3.5E)
Dark Legacies Players Guide (can't wait for the Campaign Guide to come out)
Mutants & Masterminds
Nocturnals SB for M&M
Unearthed Arcana 3.5 (I have only 3 players right now, so the gestalt rules came in quite handy)
Star Wars d20 Core Rulebook
Alien Anthology (one of these days, I'm gonna run a D&D campaign using some of those races)
Shadowrun 3E (just plain fun to read, really; small chance I'll ever run it, due to lack of interest)
Just about all of my 3.5 WotC books
Ravenloft d20
Dragonlance d20
That's all I can think of right now.