The original Call of Duty. It's bland, the characters are without backstory, there's the usual bit of destroying the entire German army on your own, and the levels suck. Wait, there is one quite brilliant exception: the first level of the Soviet campaign in Stalingrad, even though that was hampered by the fact that you're the protagonist, ergo you would make it across the Volga unscathed. Still fun for blowing off a bit of steam every now and then...