Adam's Crappy Attempt

When you start investing $19.95 to enhance the Road Rage experience, then you know you have a problem. But.. if you're ok with that, then there's Road Rage Cards. Give your horn a break and just hold up a nice sign, saying something like "I hope that cell phone gives you cancer you F'ing piece of sh*t, mother f'er." Makes a great stocking stuffer.

And it seems like most of these messages have both a semi-clean and an explicit version, for when varying degrees of rage are required. e.g.:

"Thanks for cutting me off!"
"Thanks for cutting me off... A'HOLE!"
"Stay in your lane!"
"Stay in your lane, SH*THEAD!".

And my favorite example of this:
"FU!"
"F*CK YOU!"