A cinnamon flavoured chewing gum
In gum form, it is something of a rare commodity and a luxury item amongst the student population here in Australia due to the fact that you can't buy it here. Compare to cigarettes in prison. Posession of Big Red leads to a higher position in negotiating who buys the next round of beer, game of pool, etc.
However, its pleasant and unusual flavour is not the only reason for its standing as a bargaining tool.
Like most chewing gum (in America at least), Big Red comes with each piece wrapped in foil-backed paper. This paper can be used as either a form of punishment, or a sort of challenge to prove who is the most macho, depending on the context.
With gum removed and (preferably) mid-chew, take said paper and lick the inside (non-shiny) face. Then, stick said paper onto the forehead of your intended victim (or challenger).
Oh sure, it looks silly. Laugh a little, make jokes about assimilation is complete and the metal plate in my head is picking up radio waves again. But wait a little while.
After a short time - say, about a minute - the paper-ee will begin to feel a strange tingling sensation around the paper stuck to his or her forehead. This sensation will soon spread to the rest of the head, face, and neck. It then amplifies until it seems to move into the very flesh and bones of the paper-wearer, burning and consuming, turning the base constructs of the victim into something that feels like it has been on the wrong end of a fondue stick for far too long. This sensation is highly unpleasant and can spread throughout the body all the way down to the knees.
This practice can be used as a threat - "Buy the next round or you get wrappered for 5 minutes" - or (more commonly) as a challenge, a "whoever takes the paper off first, buys" scenario. Many a paycheck has been lost, and a strange red rectangle on the forehead gained, through this ritual.
I have no idea what causes this phenomenon, but I am quite sure it is not a good thing. One wonders exactly why one cannot buy this stuff in our country.