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.
Just tried it - much cleaner than Charles for Terminal lovers like the average HN user.
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.