Spud of War
When you complete the game, you have the opportunity to play as the potato-shaped Kratos, the Spud of War. Costumes don't change the way Kratos moves or the controls of the character. This performance-enhancing costume increases Kratos's magic skills, and it also looks pretty funny.
Challenges of Hades
The Challenges of Hades are a series of increasingly hellish bonus levels that tax your skill as Kratos. The first is unlocked after completing the game for the first time, and each successive challenge is completed by finishing the previous one. These can be really tricky, so it might help to refer to a walkthrough to guide you (see Resources).
McKratos
When you complete all five Challenges of Hades, you unlock the McKratos costume. McKratos has a higher attack power than his Greek counterpart. Like the Spud of War, you'll still move the same as without a costume, but you'll have a new look.
God Mode
Completing the game also unlocks God mode, which is the most challenging of the game's difficulty settings. It will take the strength and patience of a god to make it through the game at this difficulty level.
Mime of War
The final unlockable costume, the Mime of War, becomes available after you complete the game one more time in God mode. This French-themed costume boosts Kratos's Red Orb collection. These costumes don't change the game play or the controls, but they do change Kratos's appearance.
Hidden Movies
When you complete the game, you unlock a series of extra movies. These movies don't really help you win the game, but they do give you insight into the behind-the-scenes activities of the game studio. The "Making Of" video is one of these, as well as all of the in-game cutscenes. A video about the levels that didn't make it into the game is also available, but only after completing the Challenges of Hades. When you complete the game in God mode, you can also watch a video about how the city of Attica was designed in the game, and then programmed.