basically input a series of key commands based on the weapon/ shield you use to perform a special move.

projectile deflect/ reflect- sword
you are charging up a sword and you press shield ,before its at max charge, instead of doing a charged sword atk you perform an attack that deflects/ reflects projectiles.

or

projectile cancel out- gun
you charge your gun you press shield and you automatically target the closest projectile coming at you and fire your own projectile and negate or cause it to explode before it hits you or some one near you

or
sticky bomb
when your bomb is fully charged you can press the shield button and attach the bomb to an enemy by throwing it instead of placing it on the group. when it hits an enemy it will stick to him.