OMG I would give anything to have my Gameboys back. My first was a hand-me-down original brick Gameboy, my second was the see-through purple Gameboy Pocket, and third was a yellow Pokemon themed Gameboy Color with like Pikachu and Togepi on it.
So many things. I'm a bit of a clean freak and I have a tendency to throw out old things that I think I won't use and then I end up regretting it. I've also always been the type of person to get really into certain things for like a year or so at a time and then get sick of it for a few years...