What are your "must have" webmaster tools?

We're all webmasters in our own way, what are your "must have" tools that you can't work/live without? I guess for me it's ws_ftp pro, it's the best ftp application out there imo and i'm always messing around with my server so this is almost vital to my websites management.

Other tools I can't survive without would have to be msn messenger and outlook express, communication is vital when doing business online and these tools make my life a hell of alot easier!