brotherhood_of_LAN - 7:28 pm on Oct 26, 2013 (gmt 0)
I think country, language setting and whether mobile or desktop are the main variables to consider, though I've barely looked at mobile. Those are going to lead to different flavours of 'the default'.
It then depends on whether the query is location specific or commercial as you're more likely to see local businesses based on your IP/location setting. It's possible to be top #10 in London, UK for example, but barely in the top #100 in another city in the UK. The URL in the SERP can also be different.
Then it's down to the ultra-granular user specific stuff based on cookie/account history. That's the general gist I get from checking ranks on G from many different locations, but by no means have I done a detailed analysis.