Shepherds in Northern England used to tally their flocks using a base-20 numbering system. They’d count a score of sheep using the words:

Yan, tan, tether, mether, pip,
Azer, sayzer, acka, konta, dick,
Yanna-dick, tanna-dick, tethera-dick, methera-dick, bumfit,
Yanna-bum, tanna-bum, tethera-bum, methera-bum, jigget

… and then denote the completion of a group by taking up a stone or marking the ground before commencing the next count.

These systems vary by region — Wikipedia has them laid out in pleasing tables.

(Thanks, Brieuc.)