Dislike overused fanservice. i.e. Strike Witch.
Seriously, I understand if they need to go pant-less during battle, but on a daily life as well? Come on!!
Dislike having a tune playing at the back of your mind, which you knew what it was but seem just can't get the name of it, and you can't seem to rest until you find out the name of it.
I dislike when you watch an anime for like 100+ episodes and it suddenly stops mid series with no proper ending, never to continue... *cough* D gray man *cough*