Question: What is the best proxy debugger for windows or debian?

Answer: 
On windows, I use [Fiddler](http://www.fiddler2.com/fiddler2/) for HTTP(S), which hooks up quite well with Firefox.
For lower level debugging I've used [Wireshark](http://www.wireshark.org/).
Generally I tend to use [YATT](http://www.pocketsoap.com/yatt/) - its simple and works well for me.