I keep stuff that is useful....
A couple of spare starters that I rebuilt, alternators, that I rebuilt, carburetors that need rebuilding and the kits for them. I have wire, switches, fuses, breahers, connectors, nuts, bolts, screws, nails, some electronics parts, metal of various kinds, wood, spare parts for the cars and other motorized vehicles, tubing, and pipe.
I need to get some planes(wood), brace and bits, more inserts for the lathe and mill, grinder heads for the tool post grinder, stones for the bench grinder, and extra buffer pads for the bench and hand buffers. I have all the precision tools and hand tools I need and the engine rebuilding tools to build just about any engine that reciprocates.
The inventory says I have $55,960 in tools but it is a few years old and needs to be updated. When I closed my business I sold my other tools and equipment out of necessity but I hung on to the ones I could use with 240 and 120 volts and my hand tools.
I'm not so much a pack-rat as I am frugal. I buy spare parts on sale and store them for when I need them. Belts, hoses, brake parts, and tuneup parts are stored for a time when maintenance is due.