Which shell do you use?

We had a discussion at work today about which shell everyone uses.Everyone has their preferences. There are quiet a few to choose from: sh, bash, zsh, csh, tcsh, and ksh to name just a few. I use BASH and I don’t have a reason better than it’s the default and I have gotten used to it. One feature I love is

sudo !! #this will repeat your previous command as root

Which do you use and why?