While the Master Ball is a staple in most Pokemon games, it's notably absent from Pokemon Colosseum and its sequel, Pokemon XD: Gale of Darkness. This decision was likely made to emphasize the game's focus on capturing Pokemon by using the "Snap" system, which involves weakening the Pokemon's resolve rather than simply knocking them out.
The lack of a Master Ball in Colosseum and XD adds to the game's unique challenge and encourages players to master the art of capturing Pokemon without the help of this overpowered item.