An IBM PS/2 that I've been hoarding since it was in use (that's how I got my M, and appreciation for keyboards)
A server rack in the basement complete with Xeon servers, industrial-grade switch and UPS
My uncle's slide rule
My grandfather's physics textbook
Signed copy of "Free software, Free society"
Collection of DOS games and id Software FPSes
A self-hacked, overclocked SEGA Genesis with S-video out
A GameGripper for my old Droid
XBox 360 racing wheel
Every Futurama episode on DVD
And, lest I forget, a NetBSD bumper sticker. Ultimate nerd shame.