I often use z as a temp variable when i need something to compare to when creating new code but don't want a separate window to the side or to experiment with something but don't yet know what the result can or will be. I use z purely just because i know z is very very unlikely to have been used elsewhere, and if for some reason it has, then i just name it 'zz'.

This is actually temporary by the way. It does not stay in my code. Once I'm done with it, i delete it.