When using a weapon that goes through an enemy, press the Select button (this pauses the game with out bringing up the weapon menu) when the weapon is making contact with the enemy. While the game is paused this way the enemy will continue to flash. When the flashing has stopped, press the Select button again to un-pause the game and the weapon will 'hit' the enemy again causing more damage. You can do this trick repeatidly with many of the bosses making them very easy to beat.