SkS, SS, SwS, LoZ:SS, LoZ:SwS, ZelWii, multiple others that I can't think up (yes, I just made some random thoughts). I don't think any others 'sides SS and SwS are commonly used, though.
Personally I don't even use 'LoZ' when referring to Skyward Sword. If I'm on a CoD video/forum, I write out 'Skyward Sword' (or sometimes, Zelda: Skyward Sword). If I'm on ZD or any other Zelda fansite/video/forum, I usually just write SS.
I garnered some replies that made sense, actually. I was more comparing game quality than trolling, so I suppose that's why they responded nicely. Plus, I'm sort of (not really) well known with the CoD community as I've helped a bit of people learnt he game :3
Anyway, back on topic, I think the only other commonly used abbreviation for Skyward Sword would be Zelda Wii, but that isn't even an abbr. by my standards.
I tend to use SS, I really don't see how it matters though.