your favorite debugging tool?

[Esmail]

Hi all,

What is your favorite tool to help you debug your
code? I've been getting along with 'print' statements
but that is getting old and somewhat cumbersome.

I'm primarily interested in utilities for Linux (but
if you have recommendations for Windows, I'll take
them too :)

I use emacs as my primary development environment, FWIW.
Someone mentioned winpdb .. anyone have experience/comments
on this? Others?

Thanks,
Esmail