I work with enough code that does not follow pep8 (that I cannot fix) and would like syntastic to not use the pep8 syntax checker. Any way to disable it?
If your are using flake8 as a python syntax checker you could do it like this (put it into your vimrc or ftplugin/python.vim file):
let g:syntastic_python_checkers=['flake8']
let g:syntastic_python_flake8_args='--ignore=E501,E225'
You need to silence each error class explicitly (and cannot disable pep8 checking as a whole). See the flake8 documentation and pycodestyle documentation (used to be pep8) for all error and warning codes.
Adding to Christians answer. You can also add specific checker args:
let g:syntastic_python_flake8_args = "--ignore=E501 --max-complexity 10"