A warmup for concentration.
All players position themselves in a circle. In circle will now be counted upwards, player 1 says "1", player 2 says "2", etc.
However, when it's a player's turn, whose number includes a 7 (such as 7, 17, 27, etc.) or is divisible by 7 (as 7, 14, 21, 28, etc.) he says "bang" instead of the number.
When a player makes a mistake, the group starts counting from the beginning.
A string is, for example, "1-2-3-4-5-6-bang-8-9-10-11-12-13-bang-15-16-bang-18 -... etc).
The game then accelerates, to force the players to fail.
Take other numbers instead of 7 (5,6,9). More numbers are introduced (7 and 8!)