Cropper is a great screen capture utility tool. It is completely written in C# and is listed on CodePlex at http://www.codeplex.com/cropper.
The tool is written by Brian Scott and the basic commands for using the tool is listed at http://blogs.geekdojo.net/brian/articles/Cropper.aspx.
This is highly useful for documentation purposes which needs screenshots, code snippet images etc.
Nice tool Brian...:)