This really winds me up when I got into shops. Huge signs saying "Half price on all Herbal Essences Shampoo and Conditioner" or "Half price on selected vitamins and supplements". (Boots seems to be a particular culprit).
Surely it's "All Herbal Essences Shampoo and Conditioner Half Price"? The "on" doesn't need to be there at all.
"2 for £2 on X" and "Buy one get one free on X" are a bit annoying too - surely it should be "2 X for £2" or "Buy one X, get one free". But "Half price on" winds me up the most.
Tell me I'm wrong.