There's a reason this entry isn't higher up the list, and that's because, to be fair to the BBFC, A Serbian Film is an absolutely vile work of cinema, depicting a retired porn star's quest to complete "one final job", which has him fornicating with corpses, and subjecting himself to the most lurid forms of torture imaginable. Worst of all, there's a scene which simulates a man having sex with a baby, a scene so outrageous it caused the film's premiere at London's Frightfest to be cancelled - Westminster Council refused to show it - and the BBFC to subsequently cut 4 minutes and 11 seconds from the film's run-time.
Though the film is an abhorrent piece of work in many ways, is this enough to warrant it being chopped to bits? Is the film likely to cause harm to those over 18? It's disturbing, but nobody is going to be mentally scarred by it. Does it contain behaviour likely to be imitated? Absolutely not. What the BBFC fails to realise is that the gore-hound audience for something like this is watching it for all the shocking scenes, and so to neuter the piece so drastically completely removes the incentive to even check it out. The type of person who will watch A Serbian Film knows what they are getting; they do not need a baseless moral arbiter telling them what they can or cannot watch outside of what is legal and what is not. Was an actual baby raped for A Serbian Film? Of course not. Is it revolting all the same? Of course, but that should be a filmmaker's right, to shock, to provoke, and sometimes to offend.