Linux
As a daily user of Linux and as a Linux System Engineer at T-Systems Alpine, Linux is an essential part of my geek and work life. The only reason I still have a Windows Box is for gaming.
Opensource
OSS is a major part of my life and if ever possible I try to use open software. I also strongly believe that open source is a great way to push forward invention. Most of my own development is also OSS and is available on my GitHub profile.