I'd like to see the ability to tag users in posts (@Zikara to tag Zikara, for instance.) Would work the same way as facebook (don't hate it just yet haha).
It would turn the username into a link to their profile and it would also send them a notification. These notifications should be disable-able from the account settings. The reason I'd really like this is that there are many times where I feel like a user belongs in a thread but might not see it. Rather then send a PM each time, this would be a lot more convenient.
I would have used it to notify Alex about the FWW post, to notify Zikara about a recent AEF post and awhile ago to notify madglee about a post I thought he'd be interested in, among countless other times.
Low priority.