Either hunting the ocelot unit in snake eater (if you count that, I certainly do) or if not the first boss battle proper with ocelot where you're separated by the gorge. Like most metal gear boss fights there are a million details which can go unnoticed but almost all of them pertain to something that gives you an advantage. For example:
There are three beehives hanging from trees throughout the level. No matter
where Ocelot is when you shoot them down, the bees will chase him and stop him
from shooting, this is another great opportunity to shoot him. If you shoot
off his hat, he will go and pick it up, shoot him when he does this.
Second, if you look to the left of the large tree in the middle (on Ocelot's
side) there will be a goat eating there. If you shoot it, one of the soldiers
will say, "What was that? Show some respect!" and Ocelot might yell, "Son of a
bitch!". Some of the dialogue during this fight will be different based on
your actions.
You can also toss grenades over there near Ocelot. He will try his best to
avoid them, so when he tries to roll out of the way, you can probably get a
shot off while he is distracted.
The best advantage though, is when he has to reload. After the first mini-
cutscene where Ocelot says "You won't get away from me!!" (this happens after
he uses all of the ammo from his first gun) there will be a second mini-
cutscene after he uses all of the ammo from his second gun. The cool part
about the cut-scenes though, is that you can skip them, but still hear what he
says. So instead of watching him reload, press X and shoot him while he is
still talking! This is where you will get most of your hits from, is when he
is reloading. If you shoot him once while he is reloading both guns, he will
run all the way to the big tree in the middle. If he is far away from it
though, you can shoot him a whole bunch of times before he gets there! If you
are low on health though, this is a good time to hide and crouch to gain some
of it back before he is done reloading.
When you get his health pretty low, the soldiers will open fire again, but it
will not last long, so ignore them. Pretty soon, using all of these
strategies, Ocelot should be easily and quickly defeated.
It's easily one of my favorites if not THE favorite.
