Released in 2008, four-player side-scrolling beat-em-up Castle Crashers has become one of Xbox LIVE Arcade's most successful games. And rightly so! Set in a humorous medieval universe, your gang of valiant, primary-coloured knights go on a quest to rescue a gaggle of princesses. It's just the right mix of action and RPG elements, with your characters levelling up the more you play. With four players around one television and a copy of Castle Crashers it's far too easy to burn through an entire evening.