Fanboys. ANY kind of Fanboy. It's okay to like something, but when someone makes a joke about something you like, or disagrees with your opinion, they WILL come out like an angry swarm of hornets and repeatedly sting you with comments along the lines of "You can't have that opinion!". The more hardcore "Bronies" are an example of this. I like the show, but you don't see me banging on about how much I enjoy it, rubbing the cartoon in people's faces, or bashing people for liking a children's cartoon (seriously, how many people here still watch Transformers? Or GI Joe? Or Thundercats even? And yet MLP is the one that gets all the hate?). All three parties are as bad as each other.
Gaming wise, it's any change in a franchise. ANY CHANGE. The most extreme being the Command and Conquer and Sonic fanbases are a good example of this. You change ANY detail and people WILL aggressively attack the company for even the most arbitrary and pointless reasons. I can understand things like DRM Protests, or people boycotting CoD because of Activision's business practices. Boycotting a game because it's introducing alien mechanics (or as Mr Sterling accurately put it recently - "don't buy Sonic 4 because the Physics aren't proper!") just get a facepalm from me.
And then there's those who go around preaching "you copied X!". Sometimes it's legitimate, whereby it's basically pointing out plagerism. Other times you get people calling out "Yahtzee Imitators" or "Nostalgia Critic Imitators". Everything has to start somewhere, hell most ideas we use these days have their origins elsewhere (in the previous examples, most modern internet critics can probably cite their influences back to someone like Yahtzee, NC or even the AVGN).
