What is the best collision detection for games

Hi, I was wondering what classes do you use for good collision detection for games and similar, I have used Corey Oneil’s CDK (Collision Detection Kit http://www.coreyoneil.com/portfolio/index.php?project=5) and an as3 port of the Grant Skinner method (http://labs.boulevart.be/index.php/2007/06/08/skinner-collision-detection-in-as3/) but here’s the issue, with the cdk the problem is that I’m using flashdevelop and the compiler is kind of strict so I have to rewrite a lot of thing that function in the normal flash compiler, the gskinner port has a problem about some null object reference.
I was wondering if any of you could recommend me some classes or tell me how do you handle your collision detection.

Thanks for reading.