Here's what I have kicking around my place:
A dusty Walkman. Remember those? Mine is from the early 90s, bright pink and totally impractical now that everything is digital. But I can't bring myself to throw it out - it takes me right back to listening to cassette tapes on long car rides with my family.
A box of childhood toys. I've got some action figures from the 80s (think He-Man and G.I. Joe) and a well-loved stuffed animal from when I was little. They're not exactly museum-worthy, but they bring back some warm fuzzy feelings.
A vintage camera. It's a film camera, and I haven't used it in ages, but there's something about the chunky weight of it and the anticipation of waiting for the photos to develop that I find nostalgic.