Well if we are talking about past items I have to bring up the best, hands down trash find of them all.
A hot dog cart.
A full working gas powered hot dog cart. Two cooking vats, a wet storage space for putting ice and sodas, dry containers for storing hot dogs and buns, a spot for your propane tank, wheels, and two handle bars.
The coolest find ever. We use it for random large outdoor activities at parks.