A Headhunter hunts down the person who pked you and gives you their ear in exchange for an item, if I am not mistaken. Example: A lvl 90 comes in a pks your lvl 75 and is like,"n00b n00b you suck!" and keeps killing you. You then hire someone to go in with their awesome dueler and they find them and kill them many times over and give you the ear.