There are probably hundreds and hundreds of things.
But in the interests of not becoming a pet hate to others, I shall be brief.

1) The tabloid use of the word "tot" to describe small children. I cannot describe exactly why but I absolutely fucking loathe it.

2) Bob Crow. I loathe this man on a molecular level. The physical pain I would inflict upon him given the chance knows no bounds.

3) Local Radio. BBC Three Counties radio makes the Daily Mail look like the Village Voice. Never have so many ignorant, angry racists been given carte blanche to spout crap at length (why do I listen you ask?- alas, I need the travel bulletins).

4) If you are seeking technical support on a product, WHY DON'T YOU TELL ME WHAT THE SODDING PRODUCT IS? My psychic abilities wane on contact with morons which leave me unable to automatically guess which of the dozens of speaker designs we've built over the years you are attempting do describe ("they're the brown ones with the three drivers, you must know the ones I mean.")
(Leonard Hatred briefly did some work on, Sun 4 May 2008, 14:45, Reply)