Thanks to Anic on MSE for this one.
Boots currently have Right Guard deodorant 250ml cans on a 3 for 2 promo at £2.45 each.
However if you take 6 cans to the till there is an error that will only charge you for 1 can.
I have just bought 18 over 3 transactions in Darlington today for £7.35.
See link (click on GO To Deal) for details on MSE.