This is one crossover we didn't see coming. Zombie Army Trilogy brought in some familiar faces to go against zombie Hilter and his undead army.

All 8 survivors from Left 4 Dead 1 & 2 bring their zombie killing expertise to the front lines in Zombie Army Trilogy. In case you're wondering how the Left 4 Dead folks are fighting zombies in 1945, there's a free downloadable comic that comes with the free patch that explains everything.

This free update comes with all the PC version of Zombie Army Trilogy.