As noted in the book, movies have gotten incerasingly violent over time, including the number of violent acts depicted, the number of graphic violent acts depicted, the number of killings depicted, and the number of graphic killings depicted.
The genre of movie that leads the pack is "slasher" films. Here are the body counts for some well-known slasher films.

A new one is coming out -- Scream 4 -- and it promises to feature even more blood and guts.
Now a film scholar has developed a formula to predict the number of killings in slasher film sequels.
Let B be defined as "body count":
B = 2n+12(Z-R)+2c+2S+3
B = Approximate onscreen body count
n = The number of the installment in the series
Z = Zombie factor (i.e., is the film directed by rock-‘n-schlock auteur Rob Zombie? 1 for yes, 0 for no)
R = Is the film part of a reboot? (1 for yes, 0 for no)
c = The number of colons in the title
S = Does the film take place in outer space? (1 for yes, 0 for no)
Using this formula, the author predicts a body count of 11 for Scream 4.
If you see the film, keep count and let me know if it is accurate. I'll save my money for a better film.