Hell, Just would like to know what do you guys think is the best captcha control in C# 

here's a couple of links:

http://www.codeproject.com/KB/aspnet/CaptchaImage.aspx

http://aspguy.wordpress.com/2009/04/09/creating-a-captcha-control-part1/

Besides , i found that free captcha at http://recaptcha.net/ is also being widely used on many social networking portals.You can customize it and it has C# version as well.

 There is a nobot control in the ajax control tool kit

tutorial here

http://www.asp.net/learn/Ajax-Control-Toolkit/tutorial-32-cs.aspx

don't forget to mark as answer if this helps