My cat has a few habits that give me the rage but the most annoying one is when she uses her litter tray - after she has 'been', she will spend ages just mindlessly scratching the surrounding areas with her paw. This includes the walls behind her tray (it's massive corner one because she is so messy), the edges of the tray and occasionally the actual litter in the tray. I am then subjected to listening to the extremely irritating sound she makes, which goes on and on and on..!!
When she eventually stops, I'll start to relax, only for her to then go back and start all over again!!
To make matters worse, she never actually covers up what she has done, which is what this behaviour is supposed to be for. In the end I have to go in and interrupt her and she just gives me a look which says 
Anyone else have a cat that partakes in bizarre, mindless behaviour that gives you the rage?! 