Hmm well lets see. I would have to say... my whole collection of Stargate SG-1 stuff. I am a HUGE Stargate fan. I basicaly grew up watching the show.
Here is the list (Screen used):
Ancient Communication Stone (One of three, used in SG-1)
Asgard Stone
Zat-Gun
Small collection of Replicator blocks
Sodan Cloaking device
Locator Beacon
Ohh and I know they aren't props but autographed photos of almost the whole crew.
I'm waiting on an R-75 bug and looking for Tok'Ra communicator/Bio Sensor and Autographs from RDA and Amanda Tapping