It's funny how I can go to the surplus place and find a little tool, and think "oh, that's useful!" I have all sorts of little tools I picked up that way that make my life easier, like a magnifying sheet, etc.
But the thing I use the most? I picked up an old emulator and took it apart. The most useful parts I got out of it were two powder-coated metal trays with rubber feet. They are PERFECT for holding a board over when I go over it with a hot air gun - the parts just fall out and right into the tray, and since it's metal, it's a great heat conductor and the parts stay relatively unaffected. The trays were originally for holding a circuit board to hold the chips in to program, but they're one of the few things I use every single time I sit down at the bench. Another useful things are those docks for holding laptops in with the CRT stand, they make excellent test equipment stands and even have room underneath for storing screwdrivers, breadboards, etc. They're rated at 100 lbs so I'm more likely to screw up the table before I break those. I'm probably going to go to the surplus shop tomorrow, take advantage of their sale, and pick up a whole boatload of little plastic vials for storing screws, parts, etc., in.