Well, this is not the most practical mod to the truck, but it makes life more fun from time to time. A little while back I picked up Federal Dynomax MS100 100 watt police siren speaker on Ebay for $70 and later came across Sho-Me sound controller with amplifier for another $65. This was a steal, so i picked it up and installed everything on the truck in case I ever needed to make any noise. Speaker is the same exact unit you see on police cars or ambulances it is pretty heavy and required some heavy duty brakets and was bolted up to the radiator support:
The sound controller is hidden in the little storage compartment next to the shifter. You never know its there until you open it and its very easy to reach. It has 3 siren optins - Yelp, Wail and Horn:
The amplifier is sitting under the driver's seat and is drawing power from rear sig lighter wiring:
It was a pretty easy install and most of the time was spent figuring out how to mount the speaker. About the use of this set up - well, there is really no practical purpose since it is very loud - sounds just like an ambulance or police car, so its easy to get in trouble if the cops see you messing around with it. A few times it came useful chasing some extremely slow cars off the left lane on the highway after I was stuck behind them for a while and they just kept ignoring me. A few times it helped me put an end to erratic driving by some teenagers racing each other on the highway. Usually you see these guys weaving in and out of traffic coming up from behind as they try to pass each other. As soon as they passed me from behind, I flipped on the Wail (police) tone for a second and you should see them hitting the brakes in a hurry! They usually get lost on the next exit. Other than that I try not to draw much attention and stay out of trouble.

Gutsy. Pretty sure that mod breaks multiple laws depending on where one lives. That aside, you really need to post up a video of the thing in action I've only ever seen a few emergency vehicles overseas (Pathfinders) but never saw them with lights flashing & sirens blazing.

Back in high school, my best friend & I would be in his Landcruiser and would mess with some of the house parties we got wind of in school. His dad was the top dog in law enforcement (I'll leave it at that so as not to get anyone into trouble) & he had portable lights. We would switch them on, then pull into a driveway really fast & just sit there for a while. Loads of fun.