Complete an online co-op game.
Beat the fourth boss.
Wield the pipe in single-player or co-op mode.
Beat the first boss without dying.
Wield the knife in single player or co-op mode.
Defeat Boss 'Jet' at the end of Stage 2 -- with Game Settings set to Hardcore.
Beat the game without using a special attack.
Beat the game without continuing.
Kill 10 enemies without losing your weapon.
Beat another player on Xbox Live in a versus match.
Beat 10 opponents on Xbox Live in versus mode.
Score 800,000 points in one game -- with Game Settings set to Hardcore.
