YouTube user, There is a Canal, has put together the above video which blew us away when we first got eyes on it. The video is just basically a 1 versus 1 match of Battlefield 3, except that it is played out entirely in real life. The team has completely nailed down the character animations from Battlefield 3, to the point where it's a little alarming how accurate things like holding a knife and weapon sway while running actually look.
Some subtleties to keep your eyes out for are the medkit that is thrown out, the HUD, the red fading around the outsides of the screen when damage is taken and the brutal knife-from-behind including the stealing of the dogtags.
Kudos to There is a Canal for putting together such an incredibly accurate and enjoyable Battlefield 3. For more on Battlefield 3, check out the #1 Battlefield 3 resource at http://www.enterbf3.com/.