I've been having a look through other questions on the site and can't find one listing out some of the most widely used (or subjectively best) command line tools.
Having just installed Mercurial I'm interested in what command line tools others are using.
So what command line tools do you use and which ones do you prefer? Some reasons for why you use them and what makes it such a great tool would be really useful.
I'm currently on Windows so suggestions for Windows based command line tools would be a great help.
UPDATE:
What I'm really looking for is some software to replace the built in cmd.exe in Windows. There are lots of ways we can use this software however I'm really just interested in what replacement tools people are using. I find cmd.exe quite hard to work in and am looking for a good alternative.
UPDATE 2:
So it turns out that my wording has been slightly off. The thing I'm really asking about is a Shell or Command Interpreter. Thanks to everyone who's answered. Very helpful responses.
Perhaps what you are talking about is a shell, which is the program that gives you a prompt, lets you enter commands and execute them, and carry out simple programming-like operations like manipulating arguments, substitution, and iteration. CMD.EXE is the built-in shell for Windows.
Cygwin is a package which provides a Unix-style shell ("bash") on Windows. It's mainly intended to support a Unix-style environment (with Unix-style directories, etc.), but can be used to run Windows programs as well. "bash" is far more powerful than CMD.EXE. Pretty much any Unix-accustomed user who's using Windows has installed Cygwin.
Newer versions of Windows have a newer shell called PowerShell; I've never used it but I can only assume it's a improvement over CMD.EXE.
Your latest comment says that "Console2" is what you wanted, but judging from the project page it appears to be just a console, which is just the window program that the shell runs in (granted with features such as easier cut-and-paste, and configurable appearance). You're still probably running CMD.EXE by default in it though.