As a slight tangent, generic trademark names aren't always as generic the world over. I've never heard anyone ask for a Kleenex when the want a tissue, and from your further examples I assume a xerox is something to do with stationary or printing, and I couldn't tell you what a q-tip is without googling it.

A reverse example of something I use generically but has confused a number of people I talk to in the states is using "Hoover" to mean "vacuum cleaner". They're just called hoovers because the Hoover company made them at one point.