Ruby is good for RAD
if you want a truely proficcient scripting tool, perhaps consider node.js, as of recently it is also supported by the CLR.net (common language runtime) plus it runs on everything from mac os over windows to linux (
Node.js)
So for a powerfull compliment to C# i would recommend that.
But if your needs are for the infrequent scripting, consider PowerShell, it can even use all the .net you're ever going to run afterwards and it's comletely where the rubber meets the road on Microsoft based technology management and interaction scripting (
PowerShell)