Snowball, Yuumi's Q, and probably others
So, there's an issue with both of these that most othe projectiles don't have. For both of them, the ability plays the same effect when it misses/reaches the end as when it hits. Compared to most others, which will play an effect or sound when they hit that doesn't play when they miss or reach the end of their range.
It doesn't really have an effect on gameplay, but it's very frustrating to be used to abilities like Ezreal's Q, Karma's, Q, Jinx's w, etc. etc. having visual/audio indication that they hit (especially in brush when you can't see the enemy's HP)-- but for Snowball and Yuumi's Q to play the same animation and sound when they don't hit.
It's not necessarily a bug, but it's a very strange decision.