In the "First Trial" quest for the Blood Elf Paladin, you can kill the other Paladin that was sent to kill you multiple times. Light the brazier and he will run into the cave to attack you. After he is dead, light the brazier again. The same Paladin will run in again. You can repeat this as many times as desired, earning experience each time, until you turn in the quest. This does not affect the rest of the chain, as no matter how many times you kill him you will only need to resurrect him once.