I'd say children crying, or anybody crying really, or moaning in pain.. but I actually like certain sounds of children crying sometimes. Not because I want to see them suffer, but because it's like a release for me.
A screaming/crying/very tired toddler at Target (or any store) right around 5pm or later. I always feel so badly for both the child and parent. Both have had a long day at that point. 😔