Update: Now includes tested Cho, Janna, Kayle, Malphite, Rammus and Warwick.
Notable things include the fact, that Malphite's Ground Slam pops your shield, but still damages and debufs you!

Should have Amumu and Twitch tests done tomorrow. Corki will be done when he is given out. Sion when one of my friends buys it, maybe next week. Don't know about Mundo, Kassadin, Nidalee or Udyr yet.

I've got corki and would be willing to test, but I doubt it works on most of his abilities... it would probably block missle barrage if it hits just sivir, but valkarie just leaves a damage terrain that hurts to walk through, i see no way that it could be blocked, and if it could, it would likely still hurt you after the first second.

Some of these other ones I'm not sure are right... Amumu's tantrum and despair shouldn't be blocked as they are aoe effects (not sure about his ult, but that is more likely it can block)

Finally as karthus, to my best knowlage SS doesn't work on Lay Waste... I haven't tried as Sivir, but as karthus I have seen a sivir walk onto it and take the damage without the shield breaking

@xahhfink6
The Not Testes champions (Corki, Amumu) may be wrong, but I'm 100% of Kanthus, since I tested him yesterday.

EDIT: Updated with Corki.

Updated with Amumu and Twitch. In case you missed it, I updated Corki as well.

i'm fairly certain that Corki's missile barrage is like Ashe's Crystal Arrow in that it spell shield blocks it if Sivir is the primary target but not if she's in the AoE.

Update:
Clarified one of Pantheons skills, and updated with Sion, Nidalee and... I think one champs I forgot ^^;
Anyway, only Mundo and Udyr are left, and a friend of mine already got Mundo.

Good Post

Spear from pantheon is NOT blocked.