Qtile, just because it's Python-based.
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Xonsh. For basic use (running CLI programs with arguments) it works like any other shell, and for other uses it has nice Python syntax (and libraries!). For example, I like not needing a separate calculator program, as I can do maths directly in the shell with an intuitive syntax.
I like Terminator for its mouse-controlled multiplexing. I also like the fact that it's made with Python, although I haven't utilized this fact in practice.
It me.
I've got used to XFCE.
Well, Python is my main programming language, so things being made with it gives me a feeling that I can understand and control them. Sometimes this feeling is even right, for example with Qtile, which is also configured with Python.