Magical Fortune
(Complete Scoundrel, page 79, DnD 3.5)
[Luck]
Even you are sometimes surprised by how well your spells work.
Benefit
You can expend one luck reroll as a swift action to reroll the damage dealt by a spell you have just cast. You can expend two luck rerolls as a swift action to reroll a caster level check. You gain one luck reroll per day.