I'm sorry if these exist or are discussed elsewhere, but the search feature didn't show any results. I still don't know where to put up any hacks, but I haven't really looked around yet.
Flag Down A Mod:
Kind of like the Report This Post To A Moderator feature. A user could flag down a mod or an admin and type in a brief comment. On the Forum Summary page, a red flag is displayed for the mod/admin, who can go in and see what it says.
Kick/Boot:
I know this does exist, but does it exist for UBB 5 at all?
E-mail Change Verification:
I've seen many problems with people changing their e-mail address, but it ends up being the wrong one, or something along those lines.
Require a second field to confirm the new e-mail address, and possibly send a confirmation e-mail to the old address to authroize the change in e-mail address. This might cut down on people making errors, as well as people trying to get someone's password by passing themselves off as a given poster.