Never seen MITMproxy - how does it compare to Charles? I've found super interesting stuff - pretty much invariably find that (a) there's cool stuff you can do and (b) the app's developers haven't gone to significant lengths to stop you doing it.
MITMproxy is much more flexible--but steeper learning curve. Very command line-y versus Charlesproxy. I'd use charlesproxy for casually look at apps, and MITM if you needed more advanced stuff.
