Mirror Shield
The Mirror Shield is Pit's Down Special Attack that makes him take out a shield that reflects projectiles and prevents any damage done in front of him, as long as it hits the shield. The reflected projectile does more damage than it would originally. His forward special is a faster reflector. It is very good protection against an attack that has a startup lag, such as Captain Falcon's Falcon Punch or most forward smash attacks. Unlike other Reflectors, Pit actually says something whenever he reflects something.
It may also turn around enemies, similar to Mario's Cape, if the shield is attacked directly during initiation.
Pit will put his shield away after about 15 seconds.
Another interesting thing is that you can angle up the shield a tiny bit. This has no effect on reflection though.
The Mirror Shield is one of the three sacred treasures Pit needed to defeat Medusa. It is based on Greek mythology, where a mirrored shield is used to defeat Medusa by looking at her reflection in it rather than her.