Updated Amumu Q + Spellshield Interaction
With the recently updated Amumu Q (namely, the fact that it now follows targets that leave the original area) I believe it's time for Riot to look at the interaction between pull skills and spellshields. In certain cases, such as if Thresh's Q is blocked by a spellshield, he is unable to follow up by dragging himself to the enemy champion. However, this is only because it's a double cast skill. Because things like Amumu Q and Leona E are hard CC + a pull wrapped into one.
With Amumu now following you despite negating the CC and damage, however, I believe it's time Riot looks into this interaction again and considers blocking the pull if the ability is negated by a spellshield. It feels great to build a Banshees or Edge of Night, properly use it to block a Q, and still dying because Amumu is able to follow up with his R. It makes the spellshield feel absolutely useless.