It's gotta be Black Hawk Down, there are 3 seperate commentaries:
1 - Director Ridley Scott and Producer Jerry Bruckheimer
2 - Author Mark Bowden and Screenwrite Ken Nolan
3 - U.S. Special Forces '93 Somalia Veterans
The 3rd commentary is just amazing, the soldiers talk about their experiences and how they were feeling at that particular moment in the battle.
They also correct stuff and talk about how things were different in Mogadishu because although Black Hawk Down looked A LOT like Mogadishu, it's not exact and they pointed that out