Someone who plays nothing but elves in tabletop or computer RPGs (such as Dungeons and Dragons), and has gotten to the point where they refuse to play a character of any other race.
They are a compendium of lore when it comes to anything elven about a given setting, but they get offended if one plays an elf in a manner they consider incorrect or improper.
They typically play elven females, even if they themselves are male, on the grounds that "they are more attractive to look at when playing".
Player 1: "Hey, what is up with Player 3?"
Player 2: "Oh, he's a career elf. Just let him spend time with his little elf friends and leave him alone."
Player 3 (Career Elf): "I am a great roleplayer, even though my character is born from the depths of Mary Sue-dom, and I only play one race exclusively!"