♥♥♥♥, seriously!

US Campaigns: Left Behind, Blood Tracks, Dead Before Dawn DC, Death Aboard, Detour Ahead, I Hate Mountains 2, Highway to Hell, One 4 Nine, Source of Infection, Suicide Blitz (there are two versions out, the custom Tank one is better IMO over the 'take a stand and wait for the helicopter' version), The Return: Escape from Louisiana.


China Campaigns: Wan Li, Blight Path, True Fangshi (Played in that order makes sense).


European Campaigns: Tour of Terror, Warcelona.


Random Campaigns: Golden Eye 4 Dead, Infected City, Questionable Ethics.





Also something to mess about with if you get the chance...

http://www.youtube.com/watch?feature=endscreen&NR=1&v=DCsCkqTdbNc

... this is the most simple 'How To' guide I've seen, and will defo have a try at it.