A higher tier of drinking buddy. Promote your best drinking buddies to this status when they have singlehandedly cleaned up after everyone, carried you, kept with you through absurd benders, offered to be your wingman, covered your tab, gotten you out of serious jams with the police, et cetera. You can also promote just to distinguish the few good pals from the other 95% of douche bags that you end up drinking with. Use at your own discretion.
You: Man you were clutch last night. Thanks for being my wingman and taking care of my beers. I knight thee, drinking ALLY!
Ally: I'm honored. So, when do we drink again?