Digital games offer a variety of collectible objects. We investigate players' collecting behaviors in digital games to determine what digital game objects players enjoyed collecting and why they valued these objects. Using this information, we seek to inform the design of future digital game object collection interfaces. We discuss the types of objects that players prefer, the reasons that players value digital game objects, and how collection behaviors may guide play. Through our findings, we identify design implications for digital game object collection interfaces: enable object curation, preserve rules and mechanics, preserve context of play, and allow players to share their collections with others. Digital game object collection interfaces are applicable to the design of digital games, gamified applications, and educational software.