Postman's Hat: This mask is acquired after you find a way to release the postman from his duty before the moon hits Termina. With it, you can actually check the mailboxes.
All-Night Mask: This mask allows you to go all night with Anju's grandmother ... without falling asleep. You think I'm joking, but I'm not ...
Blast Mask: You can blow things up with this mask, but be aware, it hurts Link when you do. Actually, if you hold R when using it, your shield will block it.
Stone Mask: This is an awesome mask. You can become invisible to enemies and most people.
Great Fairy's Mask: The mask with the pink flowing hair will sparkle when you're near a fairy, and the fairy will even come to you when you release it.
Keaton Mask: These were popular long ago. You can summon the ghost of Keaton with it ... be be careful, if you do, he'll put you to a test!
Bremen Mask: Ever want to dance around and have animals follow you? Now's your change, with this mask.
Bunny Hood: This is the best mask of the bunch. It increases your speed ... and time is of the essence.
Don Gero's Mask: Talk to the frog choir with this mask. If you round all of them up, they'll do a little number for you and give you something nice.
Mask of Scents: You sniff around and snort and stuff with this mask. Useful for finding smelly objects to give to people in the swamp.
Romani's Mask: This lets you in the adult-only club, Latte. All they serve is milk, and Gorman becomes the only person I've ever known to get drunk on milk.
Circus Leader's Mask: A sad, frightful mask. You can use it to keep bandits away.
Kafei's Mask: Early on in the game, you are entrusted by Madame Aroma to find her lost son. By wearing this mask, you can ask around and find out where he is.
Couple's Mask: This mask is a symbol of marriage.
Mask of Truth: Just like in Zelda 5, this mask allows you to read animals minds and talk to Gossip Stones.
Kamaro's Mask: You can pull off a pretty cool looking dance with this mask.
Gibdo Mask: When wearing this, monsters like ReDeads and Gibdos won't bother you. Some of them will even talk to you.
Garo's Mask: Summon some ancient ninja's with this mask.
Captain's Hat: When wearing this mask, Stalchildren will think you're their captain and will obey your commands.
Giant's Mask: You can only use this during the battle with the Stone Temple's boss. It makes you huge.
Deku Mask: Use this to become a Deku Scrub.
Goron Mask: Use this to become a Goron warrior.
Zora Mask: Use this to become a Zora rock star.
Fierce Diety's Mask: The coolest mask ever made ... you become a huge, adult-sized warrior, stronger than any incarnation of Link you've ever been able to control. And he also has the Beam Attack, which was noticably missing from Zelda 5.