I had a set up like that, on my $200 bumper sticker mobile (covered most of it in stickers) I took the washer nozzle off some unremembered little import (early 80s Datsun I think) I bought a universal washer pump from the hardware store and set it up in the trunk. Then I put a switch on my dash and when someone would get behind me Id squirt them. I didnt do it too often though, unless I knew the person, although there was one time when a friend and I were driving through a rich area and there were 3 girls in a Cabrio behind me, it was fun watchign them look for the rain cloud. It would shoot a nice straight stream about 15 feet. Someone suggested once that I take a fuel pump and do it....hmm I have 2 fuel pumps in my garage right now.
The next car I owned was a little nicer, I tried turning the washer setup into a bleach setup over the rear tires, but I never got the aim right.
96 STX 4x4 Extra Cab
4.whoa 5-speed (rebuilt unit by Kormex Transmission - EBay seller A+ from me)
Rancho RS5000 Shocks
Bridgestone Dueler 31 x 10.5
Lakeland colormatched cap[COLOR]
Silence is Golden...Duct Tape is Silver