Protector (3.5e Feat)
From D&D Wiki
You see a ally in danger of getting shot by a crossbow, as you concentrate you feel the impact of the bolt hit you instead of your friend.
Prerequisite: Con 18+
Benefit: At will, whenever a creature of your choice takes damage within 20 ft of you, you may take all of the damage that they would receive until the beginning of your next turn
Normal: you cant do that... duh