We just massively went through all our crap so we've gotten rid of a bunch, although still holding on to old shirts, jerseys, and crap I bought in Aussie I have no use for.
The weirdest thing I'm still holding onto is a ripped half of a dollar bill. A friend and I found it while biking in 7th grade, 1998ish. We split it and made a bet that whoever could steal it from the other person owed them a round of pizza buffet and Breadoux. Every few years we'll contact each other to see if they still have it. Mine has survived my wallet being stolen twice. Once in the middle of winter where the thief ditched things one by one along a road, and I spent 1.5 hours trying to gather items out of the slushy curb.