The guy a girl always comes running back to with all her problems she's afraid her friends would judge her for. Best guy friends are different from your regular guy friends because you can talk to them them about anything and they tend to be very sympathetic and caring. Either the guy or the girl friend at one time or another complains about being in the friend zone but neither one of them actually does anything about it. Rumors often circle around that you and your best guy friend are dating and he'll often smile and respond with a shy "nah". There is often cute flirtatious tension between you and your best guy friend.
Girl: Period cramps make me look and feel like shit today.
Best Guy Friend: Aww no, you look gorgeous. I wish I could make you feel better somehow :(