Shining Imitator (3.5e Alternate Class Feature)
From D&D Wiki
Your gods have seen fit to bless you with a talent other than casting spells.
Replaces: Spell casting ability, Spell Slots
Benefit: Add: "Perfect Imitating (Su): A paladin that sees an enemy use an ability that she can learn (See: Notes), she may make a check (using her intelligence modifier + imitator level) to determine if she learns it. The DC is less if the paladin is actually hit with the technique. When using a technique learned by this ability, use her Intelligence score instead of Wisdom or Charisma and her imitator level instead of Hit Dice or Character Level. Imitator level equals one half paladin level. DC=10+(Enemy's HD)×2, or DC=10+(Enemy's HD) if the paladin was hit with what they are trying to imitate. Works with up to third level class features.
Add imitation slots (List for Levels 1 to 20):0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9