When playing as Buffy in the Sunnydale zoo level you will have to defeat 'Ripper', the evil alternate version of Giles. You could do battle with him and his clones or you could just cheat and use the tranquiliser gun found earlier in the level! When you enter the aquarium area kill the gorillas/zombie things then use your shield to get close to the spell casting vamp at the end of the coridoor. Kill him then equip the tranq gun. When you go through the doors to meet Giles just start shooting as soon as he stops talking! It may take a while but he won't have a chance to attack you at all if you keep shooting! Nice.
Once you place bunnies on the pentagrams and Anyanka comes down from floating, to quickly kill her throw hellfire at her.