Holy Sword. It's so good it's often compared to a Mineral II, which requires 5 large devil scales to make. It's awesome, well at level at least. Despite the fact that it's pretty good I have a suggestion to make it better but first let me put up the description of Holy Sword according to Wiki.
Channels holy power to turn an Anointed Cold Iron Weapon into a Minimum Level 10, +5 Holy Burst Cold Iron Silver Byeshk weapon that grants its wielder a continuous Protection from Evil effect while equipped. The holy weapon is permanent, but it's destroyed if you log out for more than a few minutes. (About 15 minutes.) The holy weapon is Bound to Character, and class-restricted to Paladin with no UMD bypass possible. It won't expire inside of a True Reincarnation cache, so you could make a pile and use them in your next Paladin life once you get to level 10.
My suggestion is to have the Holy Sword grow in power with the paladin, like Divine Vengeance. I'll leave the exact details to the Devs but I imagine they would pick from the following:
-additional good damage
-light damage
-alignment damage
-damage against undead
-damage against evil outsiders
-damage against evil
-resistance
-spell resistance
-DR/good
-charisma
-buffs related to Turn Undead
-healing amp
-buffs related to paladin auras
-death block
-AC against evil
-guards
-other paladin like abilities
My reasons for the suggestion:
1. Flavor. Flavor is fun and this is an MMORPG. Shouldn't a paladins spell improve as he gains experience?
2. Balance. Makes the spell viable at end game and can give Paladins a boost in power if not just for the under geared new players.
Why people will say no:
1. Don't waste time programming this when there are so many bugs to fix!
Programming would most likely be easy since we've seen stuff like this before.
2. It's not fair to boost a weapon that is almost free and doesn't require any grinding!
I'm not suggesting that you make it so good that a paladin doesn't need to shoot for any epic weapons. In fact, the additional attributes don't have to add damage. Also, if the Devs did make it too powerful then they can just change the spell.
3. But paladins already kick too much ass!
I know.