Novelty Flash Drives, they're always fun to see and normally the last flash drive anyone uses.

You can get some really decent wireless headphones for about that range, fantastic for kids who might not be trusted with higher price options.

USB to Everything Adapter so they never have to find that one cord again.

A personalized mousepad with a really ridiculous photo of you or some equally absurd image.

Back in highschool, I had a pared down Ubuntu bootable on a flash drive I wore around as a necklace. Had a few small games, some modding utilities, and an sftp to my laptop at home. The boot for most the computers was unlocked and I convinced a handful of teachers to let me boot it up to get things from home or play games when I had free time.

I always thought it'd be cool to make some of those with a pre-built chat room, Minecraft or a bunch of emulators. Then hand them out to the gang on novelty drives. Sort of a secret digital clubhouse they can carry around.