Look around and ask anybody if they dropped it.
Stick it in your pocket and go spend it.
Turn it into the police.
Go spend it on random music, and skateboard accessories.
A Hyundai Santa Fe
Any car with good mpg, and isnt too expensive.
Go to the skatepark
Spend the day fundraising for charity
Go to your favorite amusment park, followed by a concert of your favorite band.
Bettering yourself through dance, or hosting a dinner party.
Anything with action