In the Challenge of Atlas, after having both Hades and Zeus' Shields, head past the room with the wall spikes and across the bridge. Just before the ladder, a harpy will spawn. Attempting to lure the harpy next to the ladder and killing it will cause it to infinitely produce red orbs for its death. The amount of reds rewarded from this glitch varies from 20,000 to 60,000 orbs.
Contributed by DrakeVagabond
Hitting R2 in the following spots in the Temple of the Oracle will cause a message to appear in the sky:
• The top left corner of the map next to a red orb chest and what appears to be human feces.
• On top of the Gravedigger's dirt pile.
• Between the two pillars of fire at the entrance.

The message will read: "Surrender Kratos"
Contributed by DrakeVagabond
In the PAL release, the sacrificed soldier found in the Chamber of Poseidon is replaced with an undead legionnaire.
Contributed by DrakeVagabond
The game's developers described the gameplay as "merging the action of Devil May Cry with the puzzle-solving of Ico".
Contributed by DrakeVagabond
Director David Jaffe wanted the game to have a fairy companion, similar to Navi in The Legend of Zelda: Ocarina of Time. The fairy would accompany Kratos, but halfway through the first level, he would have grown annoyed with the fairy and killed it. This idea was ultimately scrapped.
Contributed by KidDivinegon
In the PS3 re-release, it's possible to obtain a trophy called "Speed of Jason McDonald," which is obtained for beating the game in under 5 hours. The trophy is named after Jason McDonald, the Senior Combat Designer for God of War III, who held the office record for the best speed-run for God of War.
Contributed by ThisGuyInTheSuit
There are two statues that appear at the end of the game. If you strike them, nothing happens to tell you they are of any significance. But if you keep hitting them (200-400 times) they will finally break. A scrambled code will show on screen. Decoding it reveals a 1-800 number. Calling the number will put you through to a recorded conversation between Kratos and David Jaffe, the game's director. Kratos eventually gets fed with David and kills him, ending the call.
Contributed by DidYouKnowGaming
During development, the Cyclopes had visible penises. This matched up with other creatures having bare breasts and nipples. The reason behind this was the game's creator, David Jaffe, wanted the creatures to come across as wild animals.
Contributed by DidYouKnowGaming