South-east Asian hospitality
Not only is Singapore's airport the best I have been to, Singapore airlines beats everything else when it comes to service.
Just as a side note European airlines are the most snobbish of the lot.
From my limited interaction with Singaporeans I gathered that their smiling face was not a mask but sense of beaming pride about their country that they want the whole world to notice.
Things to do: Take the free city tour if you have more than 5 hours of layover. Also try the Kongee at the noodle shop.