Sun Devotion( Complete Champion, p. 62)
Your weapon blazes with the power of the sun.
Once per day as a swift action, you can cause one of your melee weapons to glow with the power of the sun. The illumination radius is the same as that of a torch, but the light is true sunlight and affects creatures within a 10-foot radius as such. This effect lasts for 1 minute. While your weapon glows, it deals an additional 1 point of sacred (if your deity is good or neutral) or profane (if your deity is evil) damage per character level you possess to any undead it strikes.
You can select this feat multiple times, gaining one additional daily use each time you take it.
If you have the ability to turn or rebuke undead, you gain one additional daily use of this feat for each daily turn or rebuke use you expend.