1) Players who take Airsoft way too seriously.
2) When you do your friend a favour and lend them your gun, only to have them break it or lose parts.
People who don't call hits don't bother me all that much. It's kinda rare, and CA gave me a full auto function on my AEG for a reason. I find after half a mag in the face those people are much more understanding.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."