Just regarding animations,
I've gotten bugs where Vel'Koz's tentacles are all fully extended as I move around,
Final boss Veigar stuck in idle animation where his hands circle around him
Rammus being stuck in his crawling position,
Yorick and Nasus getting stuck in their Q AA animation end,
And Ahri occasionally getting stuck in mid ult dash animation after 3rd dash. (Annoying but funny nonetheless)
Anyone feel Riot kinda said "fuck it" with the bug fixes?