Arrange the objects in 4 rows with 7 on the bottom row, then a row of 5, then 3, then 1 at the top.
Players take turns to choose a row and to remove at least one object from that row.
The player who removes the last object wins the game.
Click here to download a worksheet.
Click here for an article that explains the winning strategy.
Resources: 16 small objects. Bottle tops or stones are good for this.