The horse-chestnut tree and its conkers.

Conkers is a traditional English children's game,  players using the seeds of the horse-chestnut tree.  The tree was introduced to England from the Balkans in the late 16th century, and the first recorded game of conkers was on the Isle of Wight in 1848. There are now yearly conker championships in Oundle Northhamptonshire in October, also in Ireland in Kilkenny.