Terrify and Master Yi's ultimate Interaction
Others have probably already noticed this, but in a game I was just in, during Master Yi's ultimate, Yi runs just as fast in the opposite direction due to the immunity to move speed/attack speed slows. Obviously, this is a proper interaction on paper, but I was curious if this was something which had been thought of and if there are other immunity/tenacity interactions which were perhaps not taken into account with the switch.