This comes up when Church meets the version of himself inside of Caboose's head. Mental Church claims to be Caboose's best friend. Real Church is not amused.
Church: You're not Caboose's best friend, okay? You don't have a best friend. You know why? You don't need one. You're Church! Knowing other people just waters down the experience. Live the dream, buddy!
Simmons and Grif also qualify quite nicely for this trope, even though always throwing insults or worse at each other they never stop being Those Two Guys (if not Heterosexual Life-Partners). In fact, the very first scene of the series set them up to have this kind of friendship.
The voice actors for Simmons (Gus) and Grif (Geoff) also qualify, they make fun of each other for their heavy drinking, lousy gaming ability, extreme nerdiness, etc. but they also lived together for years, have made out with each other (as a joke), and live a block down the street from each other to this day.
Doc also seems to think that he and O'Malley have this relationship by season 4. However, given that O'Malley is pure evil, his hatred for Doc is probably completely genuine.