Sniper battle versus The End is epic, you get so engrossed in it
My buddy beat it on his second try, so I went all out to get it right on my first try. I had the flu and was home, so I literally crept around the entire landscape, listening, looking, etc..
At one point, the bastard actually crept up and got me, but I slipped off a short cliff that I was right on the edge of, so somehow I got away with that and wasn't captured.
After the last shot, I realized it took two whole hours.
Hideo Kojima actually made his developers / designers read sniper books and camp on the side of a mountain. His goal was that, if he could get half the players to hate it, but have half the players LOVE it, he would have accomplished what he wanted.