For quick prototyping, Autoit is a viable option (but it is a scripting language though).
Combined with Scite as an Editor, and autoit to exe capability (AutoIt3.exe in Scite and Autoit3Wrapper.exe to actually produce exe), you have a full GUI development environment.
AutohotKey is an alternative, but based on old AutoitV2.
Still, you can execute AutohotKey scripts from Autoit ;)
Run("c:\Program Files\Autohotkey\Autohotkey.exe c:\scripts\devicesset.ahk")
While interactive debugging is not natively supported, they are (2008, but in 2014: was?) several debugging tools to facilitate the debug process. (from this ticket)
Update 2014: the "AutoEditDebugger" might not be supported:
EDIT October 2009: NB This script has not been maintained since some time in 2008. Due to some problem with the editor it crashes in Vista.