Check out
Global Threads. It will create a "sticky" sort of thread in the forums selected in vBulletin Options. The upside is that the thread and all responses to the thread appear in all selected forums. The downside is that the thread will actually be in a different forum, so clicking on the thread moves you into the global threads forum. Also, the forums selected will be the same for all global threads - no picking and choosing per thread. Unfortunately, that was the main capability our board needed, but it's still a useful mod. We're using it for rules threads and might use it to bring attention to certain threads that might be of interest to a larger group than would notice it if it were posted in a single forum.