In the popular game Call of Duty: Modern Warfare 2, "bb" will result in crouching then standing up. When done over a dead body or someone that is alive but doesn't notice you this is called teabagging. "bbbb" will result in two teabags and is usually done to show superiority and dominance or just to be a funny fag douchebag.
See also: showboat
Guy 1: Dude that guy is planting the bomb and he doesn't even see you. Take advantage of this monumental and rare occasion!
Guy 2: bbbb done.