I bought an ex RAF ambulance that I converted once. It not only came with oxygen and flashing lights, It had the 'real' horns! One night we went for a drive, miles from anywhere, just to play them. I only did it the once before removing them. It also had the flashers but they had removed the blue covers.
We have had several air horns since then but it is the sound of the mega truck horn that could prove truly interesting. With the gleaming trumpets fixed to my roof..... YES!
(No not really... such are my occasional dreams)