On my blog, guests can post comments. I need a plugin that checks the guests name before he posts. It must check on at least names already in the database and give a response like: Sorry this name is already taken, so no one can call himself administrator etc cause that name is "reserved" in the database.
A nice extra option would be to let it check for badnames also, like shithead and f*cker. Maybe to let it work with the badwords plugin or something?