While most often you'll read about actors having to cover up their tattoos for a character role, or actors being elaborately painted in order to play a certain character, there is a small number of instances where an actor actually got real body art for their job. Sometimes the art is purely for the job and sometimes it's something that also relates to their personal life outside of work.
Actor Kiefer Sutherland got his start in movies but where he really hit it big was with the television show "24." Each show is scripted to be one hour of a single day, with all the hours of the day making up a season of the show. In season three, it was scripted that Jack Bauer had to have a specific tattoo on his arm. With Kiefer already having a variety of tattoos of his own, the actor chose to actually get the character tattoo rather than have to have it created using makeup effects for nearly every day of shooting for the entire rest of the show's television run. As this is his most famous character and the show is still in production many seasons and years later, Sutherland made a wise decision.
In the first PIRATES OF THE CARIBBEAN movie, Captain Jack Sparrow is seen with a sparrow tattoo on his right arm. In the second and third movies, the tattoo is now on his left forearm. It wasn't a mistake by the makeup crew, but because actor Johnny Depp decided to get the tattoo done permanently, in honor of his young son Jack. In addition to the design changing arms, it was flipped horizontally so that the bird appears to be flying toward Depp's body and not away from it. Movie fans noticed the change but didn't seem to mind.
When it comes to portraying the character of Lisbeth Salander in THE GIRL WITH THE DRAGON TATTOO movie adaptations, there is no shortage of body art. In the books, Lisbeth is described as having a wide variety of tattoos and piercings, most notably on her face. Portrayed by Noomi Rapace in the Swedish originals and then by Rooney Mara in the American remakes, both movie actresses committed more than most to the role. While each chose to pass on getting large-scale dragon tattoos on their backs, both did actually get a number of real ear, face and nose piercings to play Lisbeth. Not only did this make it easier than having fake piercings clipped on daily (and given the amount of action in the movies, that would have been sketchy to keep in place during many scenes) but both actresses remarked how taking such steps helped them find the headspace and point of view of the character. Rooney Mara even went so far as to get one of her nipples pierced for her interpretation of LIsbeth.