Also, people who say 'random' when another word would be more appropriate.
Oh god, that one drives me insane!
Another one which drives me mad is when people talk about 'doing' a place; e.g. 'let's go to Oxford Street and do Selfridges' (or indeed 'let's do Oxford Street'). You don't 'do' Selfridges, you go to Selfridges! You don't 'do' lunch, you have lunch! 
