F3+B

F3+B is a method of creating a white line around entity hitboxes, a red line at the entity's eye level, and creates a blue line extending out from the direction the entity is facing.

Controversy
Like F5, people saw that the blue line created from the mode would give people a slight advantage, as they got an extra second or so time to react to the fact that a player was coming towards them than the other player. People began to react to F3+B the same way as they did towards F5, and the use of it became taboo as well, so all players could play on an equal playing field. [No kills were gained in the taking of this screenshot]