the only way a person could hit you is if they propelled the weights outward, or dropped them so carelessly that they bounced into you.
in either case, the person is either too irresponsible to be in the gym, or too much of an asshole to train around others.
I'd probably offer the person a $100 buyout. If not, yeah, I'd probably drop my dumbbell on his foot and act like it was an accident too.