Just for example, the Chaos Reseves addon, which allows players to automatically add and remove themselves from reserve lists and trakcs reserve EP and all kinds of thing, I know has made the officers lives much easier and their VG experience much more enjoyable, as managing all the reserves while trying to raid could be a pain for many officers.
Many have made useful addons but luckily enough not many guilds have a queue of players thanks to the population control methods of staff

Rule #1 of GMs: A decent GM is a player who will never apply for the position