Good for random parts.
Okay, suppose you bought one of those IKEA halogen lamps and the blast burns out after just a few months of use. Where do you go to buy a new one? You can ask the guys at Mar Vac and they'll help you find a replacement. They're also good if you need say, that serial DB-9 to DB-25 cable and you don't want to pay what Fry's or CompUSA will charge you. Or if you want audio patch cord to run around the back of your stereo system. Or a new soldering iron. You get the idea. There's a reason this place is so close to Caltech. Free parking in the back too!