Easiest/Hardest placements?

Hi! I've been an apprentice for a while now, tattooing on real skin for about 2 months.
I was wondering what particular placements more experienced artists find particularly easy or difficult to tattoo?
So far I've found legs (calf, thighs, feet) and forearms easy to work with. My biggest challenges so far have been ribs, sternum and stomach tattoos. I dread doing these areas again. I have a client coming in soon for a larger piece and want to make sure the tattoo will look as good as possible. Aside from the legs and forearms, are there any other areas that are easy to tattoo in terms of stretching etc?

Chest (pec region) is usually pretty easy for me. It doesn't usually develop much fatty tissue, and what does gets stretched fairly well with gravity. Even though I've been doing a lot of them, I hate behind the ear/neck tattoos. On one side you have the ear in your way on teh right of the machine and usually a shoulder knocking up against the back of your machine hand (depending on positioning). On the other side, you can easily move the ear out of the way, but you can't stretch well at all because that dam shoulder is in the way of your stretching hand.