Power Shielding

Using your shield against projectiles right when an attack's hitbox is about to connect will reflect the projectile in the opposite direction, dealing 50% damage and knockback

(L or R) right before an attack

PewPewU powershielding a Falco laser to get a laser reset
Light Powershielding(20XX)
from Kansas City/Lawerence Smashers (Kadano)
Another example of light powershielding(Credit to Kadano)
Marth uses Z-Powershielding to increase the frame window for the powershield-projectile (reflect)
from smashboards.com/posts/18512581
Marth uses Z-Powershielding to reflect a low laser from crouch (not possible with normal PS)
from smashboards.com/posts/18512581