This kind of falls in line with the weirdest memorabilia thread.
But I have a shirt and a pair of shorts from high school that I used to wear to every cross-country meet and warm up in them. They had my school logos on it and stuff. Then I got to college and didn't want to stop wearing them, and found I had a superstition about wearing them. Even though I had to wear my college warm up suit, I had my old short and shirt underneath every meet. I had to ditch the shorts since I shredded them at one race taking them off with my track spikes on when I was in a rush. Now I find myself still wearing the shirt to road races.
I think the coolest and funniest thing is I know a guy who has wore the same shoes, singlet, and hat to every Boston Marathon he has run since like 1985. He has only missed a few since then. It is so strange to see a guy wearing old skool running clothes in 2003. He has like 4 pair of the same racing shoes, the Nike road flats and this old singlet and shorts, and a Boston cap he got at his first race.