I don't know why, but 'babes' (from someone I haven't met) irritates me so much more than 'babe'.
My least favourite thing though, is someone I hardly know or haven't even met shortening my name to a nickname.
It probably annoys me way more than it should, but a guy did this recently and it really gave me the creeps - it felt as if he was trying to prematurely enforce some kind of intimacy. He was creepy in other ways too though TBF.