I also like 99.9 Mob Choir, but it looks like people don't really care about it. All they care about is Unravel from Tokyo Ghoul. I don't find Unravel THAT much interesting.
Anyways, my fav anime openings are:-
- Mob Choir (99 and 99.9) from Mob Psycho 100
- A Cruel Angel's Thesis from Neon Genesis Evangelion
- Tank from Cowboy Bebop
- Again and Period from Fullmetal Alchemist: Brotherhood