I am not aware of an alternative to PEX for testing in .NET.
There are many alternatives to the Fakes framework, such as Moq or Rhino Mocks. See here for a more complete list. Personally I use Moq because I like the fluent API, and it supports both classical and mockist styles of testing.
The Fakes framework also includes the ability to generate shims for types which are not unit test friendly (e.g. sealed types or static methods). TypeMock Isolator is probably the only alternative to this, but it is not free. Failing that you can write your own test friendly wrappers, or use some form of duck typing.
Visual Studio 2012 has a plug in architecture for test runners, Peter Provst maintains a list of plugins here. I think VS 2012 now uses vstestconsole instead of MSTest, it certainly feels a lot faster running unit tests in 2012 than 2010. NUnit has better support for parameterized tests than MSTest.