Left to Die
As a marine, you are one of the toughest, thus, you got sent to war. But, as you was being transported, you fell out of the helicopter. When you woke up, you found out that the place is infested with zombies. They run after you. Fortunately, you found some old base with some guns and ammo on it. The idea here is to kill the zombies. Each zombie kill would earn you money and you can use it to buy some upgrades. The game would be harder as you make some progress, so better buy some upgrades.