Mtg magic the gathering: can you lightning bolt a planeswalker?

You cannot directly target the planeswalker, you must target the player first and redirect the Lightning Bolt to the planeswalker. This means that if your opponent has Leyline of Sanctity (making him untargettable) you would not be able to hit the planeswalker with LB. Anything that targets permanents in play however would be able to target the planeswalker, Vindicate being one of the best as it can destroy it, or Vampire Hexmage which will remove the loyalty counters.