Someone who flips the hell out when you use a term that is not the "original" or correct term for something even though any rational person understands exactly what you mean in 99.9% of practical situations.
"Hey, did you try the bottomless clip mutator?"
"IT'S NOT A CLIP IT'S A MAGAZINE!"
"It's pretty cool how Doom was so revolutionary putting the player on a 3d plane, which looked awesome."
"DOOM IS 2.5D NOT 3D FAGET!!"
"Don't be such a terminology nazi Kyle, you know what he means."