This is a no brainer. I hate training biceps, and legs because in order for me to properly train them I have to go through a lot of pain and a lot of burning. Especially legs.
Abs are gay because its just repetitive and boring. If you have low bf% then you have abs. So why train them other than for core stability.
Which brings me to back. I ab so fucking lutely love training back. I get huge pumps and gain fairly easily from training it. It is also the only muscle group where I look forward to going balls out heavy on.
Second that. But I hate training back, it is my weakest spot. Legs I rarely train, but when I do, they respond quickly....genetically I can get away with not training legs often and they remain muscular and shaped.
My favorite is actually shoulders, but that wasn't on the list.