The Dirty Pint
This drinking game uses a central drinking glass and a coin.
Each player takes it in turns. On their turn, they put any amount of their own drink they choose into the central drinking glass (the 'Dirty Pint'). They then must toss a coin, calling which side they predict it will land on.
If they choose correctly, then the Dirty Pint is passed to the next player. He/she then adds their chosen amount and then tosses then coin themselves.
If they choose incorrectly, they must down whatever is in the Dirty Pint at that time.
The Dirty Pint is then passed to the next person and the game continues.