The most popular Linux distribution, Ubuntu offers different OS versions for various devices like desktops, servers, tablets and phones. The desktop version, a fork of Debian, is very stable, particularly due to the number of active users, and provides a lot of features out of the box, so you can start working without having to install hundreds of drivers, tools and software first. For a lot of people, Ubuntu is the most competitive free OS to Windows and Mac.
Pro Lots of support
This can come in hand particularly with gaming as the large userbase, tutorials and forums will allow one to troubleshoot any issues they have with gaming and their particular rig.