Your keys: you almost always have them with you so they make the perfect place to stash some whatever the hell you want to stash provided its incredible small like drugs, money, or thumb drives full of government secrets. Enter the $24 Snea-Key Fob Stash from Festivaults, a 1" x 0.5″ x 2″ nonfunctional key fob stash container. Not a bad idea, but why not just use your ass like a regular person? There's a reason humans still have them, after all. "And you think that's to sneak drugs into concerts and for no other reason?" Tell me I'm wrong.
Keep going for a handful more product shots including somebody determined to sneak their earplugs and ibuprofen and Tic-Tacs into somewhere.
Thanks to Julian ST, who agrees with very little skill you could also make one of these out of any existing key fob.