PHP7
Prefer OOP. Web Framework (Slim, Laravel), ORM (Propel, Eloquent).
JavaScript
Node.js (Multi-platform resource monitoring), ES2015.
Frontend
React.js (Admin tool), Angular.js (1.x) (SP), Sass, Slim.
Linux Server
Ubuntu, CentOS, Httpd (Apache2, Nginx), DNS (BIND), Postfix, Dovecot (Beginner), VPN (OpenVPN, L2TP over IPsec).
Others
C, C++, Scala, Java (Android), Python, Haskell (Beginner).