the "PAIN" involved in getting a tattoo is 100% pesonal to each person, what one persn finds not painfull at all another may be brought to tears, location of the tattoo also tends to dictate amount of pain, a tough area commonly exposed to the elements with "padding" (ie upper arm) is USUALLY less painfull than a senstive area with alot of bone and not much padding.
Ticklish areas will also hurt MORE a the nerve concentration is higher in areas where you are ticklish...
so far general consensious of people ive asked say it feels like anything frm a cat scratch to a bee sting...but as was said like anything after 10 mins on the same spot the pin becomes more and more and sometimes so intense you have to take a break.
Wrists (where the bone is) ankle and spin all hit top 3 for "oweis" RIBS seem to be the number # choice for "most painfull spot"
Soft sensitive fleshy areas like lower belly, inner thigh, underarm, and round the nipples are also tending to be "painfull"
least painfull area form the folks ive talked to is upper arm...ive not yet gotten one there so i cant tell you.
my most painful was the largest on on my shoulder blade and thats primarily because parts of it fall on very ticklish spots, those spots definatly "burned" during the tattooing.
however my pain tolerance is fairly hihg and none of the others were realy "painfull" at all, more an annoyance and i partially slept through some!
the artist also plays a part, some artists are heavier handed and they may hurt more than someone with a ligther touch.