Like Enslaved's Monkey, Planescape: Torment's The Nameless One also used his body as a mobile diary. Unlike Monkey, however, Black Isle's immortal brute relied on said tattoos to keep track of his past lives and protect himself against a long list of enemies. As a result, The Nameless One (TNO for short) became one of the more unique characters in RPG lore.
As the old-school crowd will fondly recall, tattoos in Planescape: Torment doubled as inkable armor, granting players numerous perks, defensive traits, and stat enhancements. By the time his journey was over, TNO's body became something of a living sketchbook for runes, stories, spells, and battle scars. It doesn't get much sicker (or more uncomfortable) than that.