On the interwebs, you tend to bump into a lot of trolls. Some of them are obvious, some baffle me, and some are a weird breed unto themselves. Here, I attempt to break down the different types of trolls I know. You might know some others, but this is the limit of my experience.
The Spoiler Troll - Goes hunting through mainstream sites searching for anything that might be considered spoilers for their favorite show/movie/book and gets super mad when they find what they're looking for. If they were actually concerned with spoilers, they'd just avoid articles and posts about the thing they don't want spoiled.
The Spoiler Troll, 2.0 - This guy goes to midnight showings and releases and plows through movies, DVDs, books, games, anything, just so he can be the first one to tell you that Dumbledore died on page 596. He posts screencaps and pictures of first pages, climax points, plot points, and all manner of spoilers and posts them with innocuous titles so that anybody can stumble upon them.
(Sidenote: Who thinks they could actually finish HBP in four hours? I didn't read it in one shot, but I read DH in one shot, and it took 14 hours. And I'm a speedy reader.)
The Evil Troll - Makes racist or sexist or classist comments just to see who they can enrage. They may or may not agree with the vitriol they spew, but it doesn't matter. They're spreading the hate, and the whole point is to see other people get mad.
The Fake Evil Troll - A variant on the Evil Troll, this person absolutely does not believe the vitriol, but spews it anyway, in pursuit of a laugh or a lot of hits to their site.
The Political Troll - A Tea Party member on the CNBC message boards, or a far-left-wing liberal democrat on Fox News' website. They disagree with every opinion put forth, then drop their "truth bombs" on the unsuspecting public and wait for the fireworks to start.
The Slacktivist Troll - Posts politically driven stories, memes, videos, links, and pictures. Leaves the hate-filled comments, doesn't bother to offer their own thoughts or comments. Often claims they're "just posting information, not saying [they] agree or disagree." Information is invariably outdated, skewed, out of context, or otherwise untrue.
The Devil's Advocate Troll - She disagrees with you no matter what. Takes the opposing view, just to sharpen her own argument skills. But since she doesn't actually believe in her cause, her arguments become circular and increasingly weak. She'll often shift positions to remain in opposition to you, no matter what. This person is the most annoying, to me, because you feel like you're talking to a shapeshifter who can't remember what you were just talking about.
The Angry Troll - He's just mad. Everything gets spun in a negative way. You tweet that you liked a movie? He'll tell you it was pedantic and you are stupid. You post a joke your kid told? He'll say you're boring, lifeless, and a drain on us all with your worthless offspring. Funny video? STUPID. Book review? INSUFFERABLE KNOW IT ALLS. Article about schools in your state? SHOOT THEM ALL.
The Personal Troll - Attacks you personally, for absolutely no reason. Insults your hair, your word choice, your kids, your shirt, the books you like, the people you talk to, and everything you say. Never unfollows you, comments on your blog posts with negativity, and has very little other online interactions besides bugging you all day long.
The Fangirl Troll - Of either gender, this person watches tumblr tags, youtube channels, and hashtags of their MOST FAVORITE THINGS EVER, ready to protect at a moment's notice. The girl who responds to every negative comment on a Bieber video with "no u shut up ur stupid and he is a god and i love his hair". The teen who reblogs every GoT GIF set with a "#If you hate this I will Kill You" tag on it. They seek you out, ready to extol the virtues of their favorite singer/actor/author/person if anyone dares to disagree with that singer/actor/author/person's godhood status.
The Know-It-All Troll - Everything they say is indisputable fact. They don't need to do research. They don't need to read the research you've read. They don't care that you have a degree in this subject, or that you've read more books this year than they've read since they finished high school. They get their news from real sources, like independent news sites that specialize in uncovering the truth. They quote tons of statistics, and they reference obscure facts. Sample quote: "It is a known fact that in 1969 in Brazil, doctors found the first case of AIDS in a gay man who had sex with 474 people, and it was gay sex 83% of the time."