I'm not gonna vote because my opinion constantly changes on this matter, but here are some of my thoughts.
First off, for it to be considered useless, I would think that a mask has a purpose that can't or won't be used throughout most of the game. The stone mask and blast mask don't fit in this category. You may even consider the fairy mask a non useless mask. And with that being said...
Best Looking Useless Mask - Garo Mask. Because it is a hood, it fits Link well. It especially goes good with a deku stick that is lit. Look at Link wearing that and walking slowly while playing some scary music.
Most Proud To Get Useless Mask- Believe it or not, it isn't the couple's mask. Romani's Mask was the one I was most proud of because I really wanted to go inside the milk bar at night.
Most Fun To Use - Kamaro mask. I love teaching the girls how to dance and do it every chance I get. And once that's done, I synchronize myself with their moves and dance with them. As ugly as it may be, I love using this mask.
Most Fun To Wear - I'm not sure on this one, but I'm just gonna say the Captain's Hat. It is great to walk around Ikana Canyon with authority. I feel like I'm someone important just for putting it on when in Ikana.
It is because of these and other categories that it is hard for me to say which one I like best.