The most common shell, by far, on Linux is bash. Unless you have a good reason to use an alternative, I'd suggest that sticking with bash, or the most commonly used shell by your project team (or that the bulk of the shell scripts you have to work with) uses.
The only other very common contender is dash, which is becoming more widely used by the Ubuntu project.
This really is personal preference, well, except for csh.
Wikipedia link for csh
