I don't think I've actually had a confrontational shout from a driver (except the occasional comedian seeking approbation from his chums by shouting something undecipherable out the passenger window).
However, when I've been cut up, passed too close or that sort of thing, I tend to go for the ironic thumbs up or wave. Last time I did it, I was a little concerned that the driver might think it was a sign of approval, but I'd like to hope it has more of the effect of making them realise that that was a fellow human being they drove a little too close too.
More dangerous incidents can go one of two ways. Either a volley of Anglo-Saxon or a long stare and shake of the head. I find the latter is better for my blood pressure and dignity, but sometimes the former just happens instinctively (usually when I'm in a bad mood).