The half eaten packet of chewing gum you bought just before the shop closed, but after you consumed a healthy amount of alcohol while out with friends. Discovered some time in the next couple of weeks when you find it buried in a pocket. Usually finished with glee, unless serving to remind you of a bad night previously forgotten.
Mike: Hmm what's this *digs in pocket*
Dave: Old chewing gum?
Mike: Oh no, this is lash gum, remember Chris' 21th?
Dave: Ohhh yeah....give me some
Mike: Hell no, this lash gum is sacred