Cellphone users who call you when they are downstairs instead of ringing the doorbell... all cellphones, people who think that driving and holding a cellphone at just the right angle to block all peripheral vision on that side is a good idea.
Wifi in cafes, people pretending to work at their laptops in said places.
This whole idea that saving a few seconds is somehow important in your life, and that immediate gratification is a good thing.
People who think that language is static and has 'correct' useage. For example, if enough people start using alot instead of a lot, it's no longer wrong. People who mistake basic dialect and vocalization techniques [like pronouncing ask ax] for error and ignorance. Try taking a class on linguistics. For example, northwestern USA accent forces the mouth to add an 'r' between wa and sh, creating warsh, but it's not possible to say that with that accent without the 'r'.
American English! - I'm not bothered by it normally, Americans can use it all they want, see if I care... but the amount of times Iv'e been hand coding and found that I have spelt colour right, but of course you have to spell it wrong for it to work in html or css. If google and other search engines can figure it into semantics, why can't W3?
But my real problem with American English is on Microsoft Word and other Office related products. I have a Swedish keyboard but usually work in English. Despite un-ticking the auto language detection, Word will keep defaulting to Swedsih or US English. Why in the world does Microsoft think that anybody except Americans would want to speak US Englsih, so why make it an automatic default?
I also hate the paperclip.
Nothing gets me annoyed more than people who drive SUVs, which should be renamed LUVs. Large unnecessary vehicle.