Depends on size of tattoo i suppose. If its macro you need ive always found sony PAS cameras have excellent macro.
If not then stick to the big names. Your chances of reliability are much greater.
Other than that i suspect most people will chirp in and vote for the camera they own.
Canon, Nikon, Sony, Panasonic Lumix, Samsung (some of their NV range has impressed me in the short time ive had to try them at work)