It's really a hard one to nail down but here's the one's that jump to mind immediately:
 
Ugly Ducklings - "Nothin".  It's a very weird press on Arc records out of Toronto who I believe were the parent company of Yorkville (the press you normally see).  Also, the b-side is their other big hit "Gaslight".  Nobody I ask seems to know anything about it.  I paid 4 bucks for it about 12 years ago.
 
Trashmen - "Surfin' Bird".  It's not that crazy or rare, but it's an Aussie press I bought for less than a buck at a bookstore when I was down under.  I also got Oz presses of Blue Cheer - "Summertime Blues" and Troggs - "I Can't Control Myself" and Jumpin' Gene Simmons - "Haunted House" for the same price at the same place.  All killer records if not super rare.
 
Shadows of Knight - "Shake" pic sleeve.  Found at the bottom of a box full of real shitty 80s jukebox 45s. 
 
49th Parallel - "She Says" I just really dig the B-side "Citizen Freak".