Gay Best Friend Forever... typically used by a straight person when referring to someone with whom they have a close simpatico. They click on several levels and have a lot of fun together, sharing of advice, etc. But there is no romantic interest. Can be used across and within genders.
After all the advice Ty's given one of his straight co-workers... Tom now refers to Ty as his G.B.F.F.
Diana says Michael is her G.B.F.F. at work, because they totally have the same taste in food and guys.