chipmonger
A person who has an uncontrollable habit of eating chips. They will eat their own chips, but also have no qualms about finishing off somebody elses chips if they happen to find them unattended.
Man, I was excited to eat those Doritos I got with my Subway, but when I went to eat them, there was an empty bag. I guess that'll teach me not to leave chips laying out when the chipmonger is around.