mouse support for the Z-shell (for xterm like terminals or linux console on i386). See the file itself for details on how to use it (older versions).
a getopts that supports long options à la GNU for POSIX shells
Date/time manipulation routines for POSIX shells.
A perl script. Err, no sorry, a ruby script. Or, is it a python one? tcl, expect? Simply a shell script? But, which shell? Ok, that one's definitely nerdish.
How to implement a local scope (for functions or sourced code or eval blocks...) in a POSIX shell.