gistfile1.cs

namespace CaptureSaver
{
	class Program
	{
		[STAThread]
		static void Main(string[] args)
		{
			if(args.Length == 0) { return; }

			var img = Clipboard.GetImage();
			if(img == null) { return; }

			var dir = args[0];
			if(!Directory.Exists(dir)) { return; }

			try
			{
				var file = Enumerable.Range(1, 9999)
					.Select(n => Path.Combine(dir, string.Format("Capture_{0}.png", n)))
					.First(s => !File.Exists(s));
				img.Save(file);
			}
			catch
			{
				// (´・ω・｀)
			}
		}
	}
}