I use snake_case when I write Perl and Python no matter what other libraries that I import are using. In C/C++/C#, I use snake case when the code is wholely my own, but if I'm using calls from other libraries, I stick with whatever it uses.

The Perl 6 folk use another convention that I wasn't familiar with until I took it up. Lower-case hyphenated (some-var). Some argue that it's called "lisp-case".