The current compiler for the Cobra programming language is written in Python, but I'm part way through rewriting the compiler in Cobra itself so I can benefit from increased performance, software contracts, static typing, compile-time nil checking and more. This will also remove the Python dependency for users of Cobra.
After the new compiler catches up to the old compiler's capabilities, I will be continuing with new features including optional dynamic typing. I'm a big fan of Objective-C's support for both static and dynamic typing in the same language. The developer, not the language designer, should decide how much static or dynamic binding goes on in his software.