Boom Headshot! – Only headshots will kill zombies, but each zombie goes down in one hit. Special infected also need to be killed with headshots.

Ultra Realism – Realism mode but even harder. Death is permanent for the entire campaign. Basically Realism and Iron Man mode combined.

Last Man on Earth – This is a mutation of single player mode. You will play through the campaigns alone without any assistance from computer controlled characters. Only special infected spawn, and reaching incap means death.

The Last Samurai – Another mutation of single player mode. You will play through the campaigns alone armed with only a katana, facing wave after wave of normal zombies.

The names of these modes and final gameplay parameters are not final and subject to change, and of course more mutations will be made as time goes on, however this is a pretty interesting list to start with. I’ll see you on the versus survival floor!