Seriously, this could be added as a command, and could just be bound to a sound of the devs choosing. After all, how many times have teammates stood right in front of you blocking your shots? And how many times have you needed the attention of your teammates?
To make this feasable at all in gameplay, the /mute command should be able to affect the use of the horn for players. That way, well, the freaks won't get too obnoxious.
This is probably a seldom requested item, but give it a thought. This game has a charm in being humorous, and the horn would just be the cherry on top. The thought of a train horn or an oooga horn just hit me one day. You never know when this could come in handy...
