To this day, the Colossus 13 fight had never been topped in my AWESOME list, and it will probably stay there for a LOOOOOONG time. That speaks a lot for the game. Not even the other Colossus fight (God of War 2's opening) came close. Heck, no big monster fights ever comes close!
EDIT:
I'll expand on why I think this encounter encapsulates everything that makes SotC great (minor spoilers).
For this encounter, you will be using EVERYTHING in your disposal. Granted, this isn't he only encounter like this (the sand cave is similar), but it will require you to, among other things, JUMP from your horse to the Colossus. That you have to chase down. After shooting arrows on its belly enough times. Also remember that the arrows in this game is neither instant hit nor homing, so you HAVE to carefully align those shots.
Then we get to the implications of this "fight". The area you fight in is a vast expanse of desert. If you go to this map prior to this encounter, there's nothing (as with all the other Colossi). When you are ordered by the Dormin to do so, the Colossus will burst out of the ground and into the sky. I put punctuations in the word fight above, because the Colossus doesn't fight back. The only way it can hurt you is when it burrows back to the ground AFTER you stab it enough times in its weak spot. Now who's the villain?
Also, for a game consisting of less than 30 characters (including the Colossi, with only one explicitly named in-game before the credits), the environments do a real great job of portraying life. See, even though the world is a desolate place devoid of other people (and the only entrance to it is a long bridge that gets destroyed in the epilogue), you can really feel that there was a thriving civilization in this place in the past, that for some reason, isn't here now.