I have recommended TaskPaper many times before. If you do not need the depth and breath of a tool like OmniFocus and generally like plain text, then TaskPaper is one of the best choices you can make for managing your todo lists. In particular when you can get such nice and intelligent themes like the below.
It is crafted by DataDuke from Munich (Servus!), is called 'Things Colors', mimics the colour scheme of the CulturedCode's Things and implements some conditional formatting based on how tasks are tagged. On the related GitHub page he also shares some insights into his journey and approach to productivity.
A truly neat theme!