When you are playing as Jill and you reach the Mansion Altar, after watching the cut-scene, you will have the option of either giving Barry his gun, or holding onto it. If you hold onto it, Lisa will kill Barry, and you will keep his 44 Magnum. This is the strongest standard weapon in the game (obviously weaker than the Rocket Launchers). One shot will bring down the Tyrant in the Tyrant Room!