Rug from the Big Lebowski:
Winner.
TD's oxblood jacket, being a close second.
Other nominees:
The binoculars from Rear Window
Brando's flannel from On The Waterfront
The rock that hit young Forrest Gump in the head.
R2D2
The sink from Cuckoo's Nest
The giant weighted cock from Clockwork Orange --- (so when people inevitable touch it, I can say, "No! No! Don't touch it! That's a very important work of art."
The black glove from Dr. Strangelove
Mickey's wand from Fantasia ...Wait, that's a cartoon.
Marsellus Wallace's briefcase w/ contents.
The egg from Risky Business
Andy Dufresne's nested bible w/ rock hammer.
Ricky Vaughn's wildthang glasses
Crocodile Dundee's knife (for obvious reasons)
A TreeStar from LBT. ...Shit, that's another cartoon.
Billy Baroo from Caddyshack
A JURASSIC PARK JEEP!