I'll start...
It's incredibly immature and irrational but there is a certain (fairly common) name I cannot stand purely because it's the name of both a girl who bullied me when I was young and DHs ex, who is difficult.
I literally hate any mention of this name and automatically dislike anyone with it (ok, not really but in my head for a few moments I do!).
Another less petty but more bizarre one is that I HATE the tops of bottle caps scraping on my nails. It makes me want to be sick. Shuddering thinking about it right now!
Anyone else got any weird/petty/irrational dislikes?