I've got shirts & robot parts from a few robots of ours and a few other teams.
The coolest FIRST item I have is an original copy of the
1996 Championship Elimination bracket. It is a cool piece of history seeing all of the old teams back when FIRST was just beginning.
I got it when 3467 was beginning a friend of our lead mentor was a mentor on the Salem HS team back in the day and he loved sharing old "artifacts" like these from his day in FRC.
One day I dream of it getting filled in but that probably won't happen.