The zsh port (zsh-4.3.10_3 right now) installs a couple of FreeBSD-specific completion functions. One of them, for mount(8), gives the list of devices that may be mounted (as the first argument to mount). The output from `glabel list' should be included, but isn't because of a typo.
Additionnaly, `glabel list|grep Name' doesn't include the /dev prefix; this may be because of a change in the way `glabel' prints its information (FreeBSD 7.2 RELEASE doesn't either; I'm too young to remember older releases).
How-To-Repeat: Make sure you have a device such as `/dev/ufs/something', not listed in /etc/fstab/.
Using zsh-4.3.10_3, type `mount /dev/[TAB]'. `/dev/ufs/something' should be suggested for completion, but isn't.
Fix synopsis and assign.
I'll take it.