linuxmemes

It's just the easiest distro to get into coming from windows/mac. It's more lenient about the third party/closed source software that people might be familiar with, lots of GUI tools including the Software Center that makes it easy to install things, and plenty of flavors to suit whatever feels most natural to you. It's got a nice GUI installer and live version that is sure to make people feel more comfortable about installing an OS if they've never done it before, and it's not at all fussy about the hardware it runs on. It's also rock solid as far as I've experienced. And, of course, it has the benefit of accessing the huge amount of software that supports debian. Also, owing to its popularity, the community is very active and welcoming to newbies.

When I was first getting into Linux, I was definitely more experimental and tried out Fedora just to get as far from Windows as I could. Now I'm not so adventurous and just want something that provides as similar a workflow as possible to the workflow I have to use at work with windows. So it goes that, when setting up a new laptop where I want an OS that just works, I reach for Linux Mint.