We were both smokers in the early days of marriage, and saved all the coupons - Embassy, Sterling, No.6 - and I know we 'bought' lots of things with them but for the life of me I can't remember what they were! I do remember enjoying looking through the catalogues.
And, of course, petrol coupons, green shield stamps, co-op divi stamps.
When the children were young we had quite a collection of mugs acquired from collecting chocolate wrappers - Wispa is one I remember - and Kelloggs Cornflakes cereal bowls.
More recently, Tesco have from time to time given stamps that could be used against a purchase, greatly reducing the price, and I have several things in regular use, such as kitchen knives and bakeware.