My pet hates are:
Showing people how to do something and it becomes obvious they arent listening as they go and cock it up again straight away.
People talking over you when your trying to have a conversation. Wait your turn!
Lazy folk - not so bad if the work they do is good but when they dont do anything and the work they produce is naff - I hate that.
Office politics - its not what you know but who; Cant stand it when people suck up to complete swines just cos it furthers their career.
Negative, pessimistic folk that are only too happy to point out someones flaws but do not have the ability to praise anyone when deserved. I always try to give praise 10 times more than I complain about performance, its hard but people tend to work better when they feel they are doing something wothwhile.
Nepotism!
It may sound like quite a long list but I actually do like the majority of people I work with!