I'm going to say "space marine." Think about it. Halo fans (you know which ones I mean, not all of them in general) are exactly the sort of macho-douchebags who hate on MLP fans. Further: ponies are peaceful, space marines are made for war. Ponies (we're talking about My Little Ponies, yes?) are colorful, space marines are dull gray and brown, or at least their games are. Ponies are cute, varied, and with diverse, relatable personalities, and space marines are all identical, emotionless, and characterless.
Of course, I don't mean to insult any mature, sensible Halo fans, I'm just pointing out the vast disparity in content and fandoms.