Although it has been posted about a couple times here in the past, there still isn't a really well done tagging plugin in the store. The ability to take other users in statuses would be huge for my community (and others). It would be nice if this feature spanned across the entire site (groups, comments, blogs, status etc.). There really needs to be an auto-complete feature so that if a user has the username Whateveritis... I will get an auto-complete for @Wha. Having to remember and type out full user names isn't practical. I know a lot of users would probably put down good money for a plugin that could accomplish this and simply work.