Never on Linux, not on Android, nor has Apple shown any indication of supporting Windows RT. If anything, Apple's abandonment of Safari for Windows indicates that they can't wait to support their platform solely. Even their retail store app, which is used to sell hardware products as little downside of being cross-platform, is iOS only. That's just cutting off your nose to spite your face behavior we've come to expect from Apple.

Where's Internet Explorer and Office 2013 for OS X? Which significant Microsoft apps run on iOS?

Obviously it makes sense for Google to get its advertising hooks everywhere it can, but I don't see Apple and Microsoft having the same cross-platform incentives at all.

With google forking webkit, it will be good to have safari back on windows. I could not understand their decision to quit safari development on windows. Integrate and share data between a good safari desktop browser on windows and an iDevice would be nice.

They had Safari for Windows and dropped it. And iTunes and Quicktime both run considerably worse in Windows compared to OSX (besides looking out of place).

I think that's the entire list.