I've always heard the biggest and best is the Stebel Nautilus, which is an air horn with its own mini compressor.



This "Bad Boy" is even prettier...



My only problem is I don't want to be sitting on top of a 139 decibel horn without earplugs. Are these directional?

They attach with a single bolt, and take standard 12v wiring.

I imagine these all come from China. Taobao anyone?