Attention XCOM Fans: Check out this very cool PC Gamer breakdown of Zemalf's incredible impossible-difficulty Ironman run in XCOM: Enemy Within. The guy made it through the entire game on its highest difficulty with no saves and zero casualties of any sort. Zero.
I enjoyed Enemy Unknown but I was not man enough to try and beat Ironman with all the gamebreaking bugs.
I had to restart missions close to a dozen times in one playthrough due to clearing out the whole map and somehow having enemies out of boundaries where I could not see them, only knew they were there from the visual echolocation indicator that would actually come from the boundaries of the maps.
Surprisingly this was also on Xbox 360.