I've never found sheet music that requires piccolo wah, but i bought it out of curiosity and i've found myself using it many times with wonderful results.
The stem is removable so it is also a harmon mute.
The harmon mute sounds just like an harmon trumpet, a little thinner and with more projection, it's a beautiful sound and smoothes the edges of the piccolo sound.
The wah wah mute is even more comical-sounding than a normal wah wah, leaving it open will sound a little like an oboe.
I've used it in cartoons and videogames soundtrack with amazing results, the tone sticks out without being heavy, and it is just a really distinct and characteristic sound, often but not always comical.