I either use them to line the bathroom garbage can or use them for cleaning up pet waste. I usually don't get too many of them, since I use reusable bags more often than not, but I always do my best to put them to good use when I do have them.
I put that I return them to the store, which IS what I do with the leftover ones. But I also use some of them for garbage, used cat litter, dog poo, and more!
I do all sorts of things w/my plastic bags. Everything 'cept throw them out;) Our newspaper comes delivered in a plastic sleeve. I've found a couple good uses for them. I have a zillion garden flags for every occasion that I wrap around a cardboard tube from paper towels, then slip into the sleeve. It keeps them clean, unwrinkled & they take up less storage space in a drawer. Also, I do the same w/posters my dd collects from horse magazines. Nothing looks worse than a poster that has been folded. Roll 'em & stick in the sleeve. jan