I remember garages giving "triple" or "quadruple" stamps with petrol. Company reps would get their petrol from the garages that gave the most stamps (usually the most expensive petrol) as the rep would get the benefit while the company picked up the bill: used to piss the accounts department off.

That said, I'm still using a pair of axle stands I got with Green Stamps (or was it Embassy coupons - remember those?)