Skarner's E
I've mained Skarner for a long time and many games I've found that his auto attack won't stun an opponent that has been hit with his E as intended and I have finally figured out why not.
Skarner has no cast time like other champions, he is able to Q spam during auto attacks and he is actually able to do this with his E as well. The problem is, if your AA is just starting its animation and then you cast E and it hits the champion that is typically right on top of your face, E will hit, then his AA, but the opponent does not stun until his next AA animation. There have been times where the .7 seconds in-between auto attacks have meant life or death for Skarner if both champions HP are low.
Here would be 2 simple fixes for this problem:
Solution 1) If E strikes the opponent before his actual auto attack does, then he stuns. Solution 2) (I would prefer this solution) Give E a short cast time that does not coincide with his auto attack, thus resetting his auto attack back to the beginning of the animation, allowing a stun.