Everyone's different. I've worked in several tattoo shops and had a lot of tattoo work myself. I've seen big burly dudes cry while getting their ribs and armpits done, but I fell asleep for mine.
I would say the back of the neck isn't the worst. The palm of my hand was the worst, followed by my ankle bones, alkalies tendons and shin bones.
A general rule of thumb is that the the less fat there is and the more densely packed the nerves, the worse it will hurt, but EVERYONE is different. We each feel pain and pleasure differently and there's no way to predict how badly a spot will hurt, or not.