Python
Python is my preferred language for writing tools. This is because it has a large array of libraries, a good package system (pypi), and the fact that you can easily create command line applications (setuptools). I have also used pygame to visualise topographical data provided by a Lidar device. At Janus I used Flask to create micro services that provide various automated actions based around Gitlab such as e-mailing events, configuring newly created projects, and bespoke tasks during continual integration cycles.