Don't want to damage anything or anyone-- ! Also, was sorta kidding about the smoke screen-- (But, knowledge is power!)
What I would prefer is to have something that would have little effect if the person was a resonable distance. But, too close, and... awww, crap, I just washed my SUV....
Just a light mist of double strength powdered milk. Lots of little pain in the ass dots.
I have a coffee cup holder mounted up front on my Targa. One morning a jerk was tailing me, so I grabbed the cup and sloooowly poured it over my left shoulder.
Backed off.... lots of nice creamy spots...(sugary too, mmmmm).
(Bing! the gears began turning...)
It would be pretty darn cool to build a "james bond" ped. "For off road use only...."
Maybe a potato cannon up front? Air horns, disco ball, rotating yellow "tow truck" light... etc. Super Moped.