Pistons for doorknobs.
Camshaft for pull handle on the beer fridge (can't be a worthwhile shop w/o a beer fridge)
Connecting rods can also be used as shelf braces.
Aircleaner housings as light shades.
Old hood ornaments and dash knobs as cabinet door pulls.
Old "mags" as hose reels.

There, that should get the ball rolling.