Knight Knight is a strong card to deploy near the end of a game. Though it has a rather hefty price tag with a lower attack, this card can heal itself for 3 HP every time it kills a monster. And since Beta 7.3, it does so whilst both attacking and defending.
Typically Knight Knight can kill at least three other cards before dying due to this ability. If Knight Knight has 3 HP left and then attacks and kills an enemy with 3 ATK, then it will die anyway.
A good combo with this is by giving it Taunt with Protection or Glad Dummy, so all enemies are forced to attack it, which would make low ATK monster either a sitting duck, or make them actually heal Knight Knight. Combined with Orange laser, the cards will most likely end up dead even if they don't attack.