edit--"Holy Shock" read as "Holy Sock" before I edited this. While editing to make it look nice, I HAD to preserve that typo in a note :)
A retribution Paladin's most powerful talent is Seal of Command. Retribution Paladins(or Retnoobs to some) specialize in doing damage and putting up debuffs on the target(such as Vindication and various judgements). A typical Retribution build would looking like this or this.
Protection Paladins are excellent at PvP with Reckonbombing, and Improved Hammer of Justice, along with Blessing of Kings(This is one of the best buffs you can get, as a paladin) and Seal of Command. If you store 4 Reckoning charges, use Blessing of Kings and Seal of Command, you can easily OHKO anyone in cloth or leather armor. A tanking build is not reccomended, as your only way to gain threat is by white damage, or using Righteous Fury, which is rather sub-par. But if you wish to try it anyway, a typical tanking build would look like this. If you're looking for a PvP build, look no further than Reckonbomber.