My random thought is a pet peeve: People Who Refuse To Consider A Hypothetical Situation.
Do you ever get this? You're having a conversation with someone and you say, for example, "what would you do if you broke both your arms at the same time--how would you brush your teeth, dress, wipe, etc...?"
And the other person just says, "that'll never happen." So you say, "I know, I'm just saying WHAT IF..." Then the other person goes, "that won't happen because I never get hurt. I'm very durable and well coordinated--I never get injured." And you go, "I realize it's very unlikely but it is logically and physically possible and I'm asking you to consider this hypothetical scenario for the purpose of discussion because it is interesting to me..." And the other person refuses once again to consider it even as a possibility and they go on to discuss their athletic prowess and how in high school they played sports or something and never got hurt and they're so great, blah blah blah.
People who do this make me angry.