There are certain added features like limited disposable bombs and knives that can get you out of being attacked by breaking an enemy's hold. I hope I'm not spoiling it for you, but there are new super zombies called Crimson Heads that force you be more strategic with your bullets as well as when and where you kill regular zombies because they'll come back as super strong and super fast Crimson Heads unless you burn the bodies with gasoline within a certain amount of time, but you've also got to keep in mind that there's not enough gasoline to burn them all either. There's also another big boss monster as well as an added storyline surrounding it.