The best mask ever is the Stone Mask. Monsters and attackers IGNORE you and don't even bother you, it makes you invisible to them. They treat you like a plain old boring rock and leave you alone. With that happening, who would not want to take advantage of it? I took advantage of their ignorance and attacked those beasts and slayed them with my sword. I also like the fact that this mask makes you feel like Luigi.
(Off-topic)
Why Luigi? Cause Ignorance is bliss. He is in pure powerful bliss. Just look at his Final Smash in Super Smash Brothers Brawl.