Sean Dague, who works on OpenStack, has a nice post on Emacs Python tools he uses to deal with the large Python code base of the project. If you work in Python, you’ll want to take a look at his post. You may pick up some useful ideas.
If you’re familiar with cscope, you will probably be interested in PyCscope, a project that parses your code’s Python AST to build a cscope index. The project’s README says that using the Python AST gives a much more accurate index than using cscope alone.
He also mentions fly-hack a backend for flymake that extends flake8 with some additional rules. Again, if you’re writing in Python, you may get some ideas.
Dague discusses other tools as well so you should definitely give his post a read.