I run a fairly large site so a lot of this is feedback from mods, on top of that some of these little features might already be available as I started compiling this list a while ago. Thought it would be better to categorize them and post them in one go than start multiple threads. Anyway here goes:
Registration/IP-related:- option to "flag" an IP address so that it doesn't block registrations, but makes a note that someone is registering from a flagged IP
- in "manual registration approval" mode, it would be good if the system automatically cross-checked the user's registration IP with the database and listed any correlations
- show country flags for IP on registration approval screen
- ability to select watching a user on the registration screen when confirming the registration. Make it possible so that all posts this user makes are sent to the PM-box (only the admin to have this function)
- being able to search for posts according to IP (not just registration and last post IP)
- after display name change automatically list user's old display name underneath for predetermined amount of time (option set in admin panel)
PM feature:- more PM security features, such as auto-lock of this feature in chosen groups if the system detects the same message sent to multiple recipients (possibility of spam)
- PM from admin to override any max message settings
- create PM folders, with ability to set certain messages to automatically be placed in given folder (for instance multiple-user alerts)
- ability to sweep through PMs to catch out spammers using a "PM censor list", user's PM feature to be blocked pending admin investigation
User-related:- ability to lock a user's profile in the CP (I recall UBB.classic having this function) to prevent him from updating stuff like location, home page, etc. A little check-box should do it
Posting/Forum:- when posting an internal forum link (to other thread/topic), automatically substitute the link to show the title of the thread being linked to instead
- block ability to change subject of thread with every new post
- allow post moderation not only in certain forums but also certain individual topics
- special censor list that doesn't change the text but informs the admin via PM about the post/author. Would be good if this can also sweep through PMs to catch out spammers
- ability to set a time-frame (from x time to y time) for a forum to automatically be displayed in a different location. Useful if you have a subforum about football but you want it to automatically move to the main forum screen during the weekend.
- ability to create forms for certain topics, whereby people cannot write replies freely buy can only respond by filling in a special form (kind of similar to the polling function)
- instead of excluding certain forums from a user's post count, it would be useful to give certain forums a different status so although the total post count will appear below a users name/avatar, clicking on his profile will show the total posts (in a pie chart for instance) and differentiate between those on most forums and those singled out by the admin (for instance relevant forums VS off-topic forums)
Admin/mod actions:- put deleted posts in a "trash can" visible only to the admin - sort of like a log of all deleted posts, which could be revived and put back in their place if the admin overrides the decision to delete. From a technical standpoint this could be done by making a mod's erase function merely hide the post… until the admin then verifies the deletion to wipe it for good.
- as above, maybe create a separate function called "hide" which mods would use instead of delete
- multiple post erase function: admin/mods granted this ability will see little check-boxes next to each message in topic view, enabling them to select multiple posts for deletion (similar to multiple thread deletion - but for posts instead)
- split 'edit user' features (banning/editing privileges) into separate powers (ex. allow a group to edit but not erase a user with his/her posts, some mods to be allowed to give time-bans, others permanent bans, only some or none to be allowed to delete users, some not to be allowed to even edit (or what the next suggestion below will be about - even see) any user data, etc.
- make the ability to see a user's email address (or other visible user info fields in CP) a separate privilege (just like with the IP address which is a separate option), so that for instance mods with certain editing powers (like time bans) would not even have access to people's email addresses
- log profiles looked up by global mods (or those with access to CP user profile info)
- force password change at next login: this should be available on an individual as well as forum-wide basis (for instance compromised database, where you would want as many users as possible to change their passwords asap).
- time bans on certain forums, instead of applying to the entire board
Others (logging in, posting pics via mobile phone - possibly iphone app, built-in banner rotation system):
- SSL login, CAPCHA for subsequent logins after unsuccessful login
- special page for selected users to be able to post photos from their mobile phone (iphone app?)
- including a simple banner rotation system, I would definitely pay $$ for such an add-on
- splitting us posts table so that new one is created every year (speed up database by splitting it up into smaller chunks on an annual basis, backups would also only need to be done of current db table)