Remember, who has the right of way? THE ONE THAT HAS THE LEAST TO LOSE....
Any agressive act (thowing objects, slamming brakes, kicking mirrors, obsecne guestures, showing hardware, etc.) just might get you either run over or knocked off the road dead. Is that really the impression you want to give? Waaaay too many cagers out there drugged out/drunk/wound up/road raged...and you have the most to lose..
How about something simple that's already on your bike, your emergency flashers? It won't work for long, but will cause the driver following too closely to realize you are signalling "something is wrong" and they will back off long enough for you to either get out of the way, or find an opening to speed up and move over or on.
More than once, I've used my emergencies when approaching slowed traffic to let the people know behind me to back off (works good in autos also).