I received a silver maple leaf (and sometimes the odd novelty silver ounce) from my grandma on birthdays and sometimes Christmas for years, and I now have 40-something.
Awesome Uncle Gift: Framed share of Disney. Tell the parent's it's worth $$, but tell the kid HE FUNKING OWNS DISNEY.
How about a piece of celluloid from an actual movie? Then when he's watching Fox and the Hound or something he can proudly show off the piece that he owns.