I was playing one like this out with someone, but he's been quiet for quite a while, so, I thought up this one today.
On March 3, 2015, World war 3 started, with China and Russia, along with North Korea, launch attacks on the Western countries, Europe, and the US. My character would be somewhere in europe with her unit. A Marine corps first lieutenant, she would be in her humvee in the middle of incessant shelling when somehow, the humvee and everyone in it is transported from 2015 to a point in europe in 1944. France, Holland, Germany, it doesnt matter. You would play an allied soldier, with some others, who finds my characters humvee on its side, with only my character alive.
From there, it can go in any direction. I would be out of time, but with enough future knowledge to be useful.
If this appeals to anyone, let me know.