(I personally didnt find the wrist to be painful at all) Anything directly on bone, covered pretty much only by skin, is going to be VERY painful. Its harder to get tattoos on places like your foot or wrist because your first reaction is to pull it away from the pain. Like I said, the wrist didnt hurt, but it was uncomfortable. In the end, its going to be there for a LONG time... so grit and bear it, and love the tattoo forever.
I have heard from my friend who has his entire body tattoed that the throat, wrist, and side hurt the most. I dunno about the side, and I think it differs from person to person. Personally I think the sternum would hurt like a bitch, but I am also bony as hell there.
everyone has a different pain threshold for some the pain is a high all of its own also depends on the skill of the tattoo artist getting tatts on the bones of your feet hurts a bit, well hurt me anyway another tip, if you ever want them removed you never know, laser really hurts and aviod the colour green it is nearly impossible to laser off the colour show us a pic