Any kind of unfairness, from being shortchanged at the shop, to the world's unfair distribution of wealth.
Rude people, especially people who are supposed to be service-minded, e.g. bus drivers, shop keepers, waitresses etc.
Men going on and on in the comment section of internet newspapers about how oppressed they are - no matter what the article is really about. Example: Article title 'So-and-so many thousand women are raped in wars every year'. Comment: 'Why does the feminist media always focus on women as victims, women can rape people, too, you know.'
People going on and on in the comment section of internet newspapers about how everything is the socialists' fault. Also no matter what the article is really about.
Cruelty to animals/children/people who can't fight back.
Mess/dirt that isn't mine.
People who say 'it's just a dog'.
And many, many more. I'm evidently the negative person making your blood boil