A moderator log on the front end, so my moderators can see what actions are being taken. This is incredibly useful, as everyone can see latest actions and what posts were moderated etc. I used to used the per thread one, but I did not find that as useful as a global one.
An easy way to find soft deleted posts, cause if you miss them, they might be stuck in limbo forever. This is something we shouldn't be relying on 3rd party addons, and not something hidden away in the ACP, where you have to trawl through potentially dozens of moderator actions to see if anything need hard deleting.
Maybe also a bit more WYSIWYG, hiding BBCODE all together in the editor, which includes code and quote tags. Would love to see a bit more flexibility in the editor as well, for example being able to disable some bbcode (especially font size and font color, some users are trying really hard to use colors that are impossible to read on your background). In fact, I would settle for a simple button manager for the bbcode editor, and setting the editor to paste text unformatted, because removing the button is a defacto way of disabling the bbcode.
A true menu manager, where you can enable and disable links easily on the navbar. Right now you can either add them in the middle, at the start or at the end, but not being able to choose the display order your self. Also being able to configure the dropdown would be real nice as well.