Rammus Taunt bug
Sometimes, when you taunt somebody, they walk away for a varying amount of time instead of attacking you.
This bug has actually been around for a long time, and happens infrequently enough that it's a "yo, what just happened" kind of moment, but it can get annoying when an ability's function just fails to work like that.
It's been brought up every now and then, but I do want to know if Riot still remembers this bug and is working on fixing it.