1. Widgets.
Actually I lied. I'm not going to explain why I hate widgets. 'Cause everyone else already has. I'm disturbed they still exist.
2. Blacklist conversations.
Nothing is more annoying that being dragged into a conversation where someone is claiming that someone else is sending out viruses or a perv or, in rare instances, a murderer. No, no they're not. Stop it.
3. People who complain on the forums
God they are annoying. Like anyone wants to hear you gripe about trivial junk that has no bearing on everyday life. They ought to have their fingers cut off so they can't type anymore.