PC Zone once provided a “mouse cleaner” as a free gift. It was a hard plastic thing with a short handle and a small dimpled ball on the end.
This was back in the days when computer mice had balls inside them. The idea was that you took the ball out of your mouse, stuck in the cleaner and twiddled it around a bit to get the gunk off the rollers.
Except it did nothing of the sort. I think that PC Zone actually ended up apologising for supplying such a cruddy free gift and promising that their next one would be better.
I’ve still got mine and it actually worked quite well for me to be fair.