In fantasy and science fiction nation-based roleplays: people expecting non-human species to abide by the human psychological model. 

Far from subscribing heavily to the 'hard' science fiction archetype or Starfish Alien trope, when I construct a non-human species, I want them to be distinguishable from the human norm on a predominately mental level. This causes issues in nation roleplays when war is the topic of the OOC/IC(naturally), because you're going to run into people who insist that your aliens or fantasy species must follow in humanity's footsteps when it comes to thinking and waging martial campaigns. If you aren't running space fighters or using armored knights, a fit must be thrown. 

Additional annoyance: roleplayers using the word 'race' to describe non-human sapient species native to science fiction and/or fantasy roleplays. I blame Tolkien for this one. The word only sticks if both members of the human and non-human species can produce viable young with one another (since this implies that both creatures possess enough mutual genetic material and shared-ancestry to procreate successfully); a six-limbed mantis-like extraterrestrial being that hails from the planet Zog is not a sub-variant of the human species, and therefore is not a 'race', but an entirely different species altogether. 

Stop applying humanity's notions of race to non-human specimens; stop doing this stupid shit. Fuck.