Nemerle is functional, but doesn't force that "flavor" unless you want it. This means you can write imperative code that looks a lot like C#. However, as you learn more about functional programming you can improve your coding style.
Boo is awesome. It has the right mix of static typing with optional dynamic typing. The syntax is super-lightweight, making it ideal for teaching programming to students. In addition, making domain specific languages is easy.
Both have a syntactic macro systems, enabling even higher level meta-programming (think DSLs again). (I know F# has macros of some form too.)
Both have super smart programmers innovating on their development and rich communities.
I'm not saying don't use F# or IronPython. I'm saying please take a good look at Boo and Nemerle as well.