After providing CPR to a few people and seeing them not survive with all their faculties, plenty of paramedics and nurses joke that they're going to tattoo "DNR" on their chests rather than suffer a similar fate.
The joke's on us. There are now plenty of people doing exactly that.
The problem is whether or not it really means anything. I can appreciate a person's desire to bow out gracefully and skip the old pump and shock, but can emergency responders really ditch CPR based solely on a little body art?