On Win32, with unmanaged code, the return value is usually stored in the EAX register. This is useful when the program doesn't save the return value in a variable. This can easily be seen in the Visual Studio debugger.
Is there an equivalent for managed code?
It is true that the JIT compiler will still use the EAX register for simple value types, that trick requires enabling mixed native and managed debugging. The truth is, there's no simple way to do this in Visual Studio at the moment. This is something being considered for a future release. Shall I consider this an official request? :-)