Well, I have amassed quite a bit of random stuff:
I have several spent .50 cal training bullets from a disused WWII-era bombing range we explored. I also have a 'No Trespassing' sign from said range.
I have four Cold War era radiation dosimeter pens. Interestingly enough, all of them show significant, though differing, radiation levels. I'm fairly sure it's just age... at least I hope so. I also have a "Fallout Shelter" sign and a couple of biological and radiological defense manuals from the same era.
I've got a little chunk of obsidian from when my family was visiting Hawaii and Kilauea happened to be spewing lava across the park road.
I've got a piece of driftwood that managed to tie itself in a knot before drying out. I don't remember what camping trip I got it from, but I have it.
And lastly I have a stuffed animal from one of those grabber vending machine games. Won it on my first try. I can therefore claim a 100% success rate with those games.