This would be a chat and not shoutbox; I understand there's a difference (although I'm still not clear on what the difference is).
It would need to be real-time with a refresh of no more than 5 seconds.
I currently use one created by these guys for phpBB: http://www.startrekguide.com/
This is what it looks like when logged in.
It is fully integrated into the forum so once logged in to the forum you can use chat.
All smilies and BB Code are available and most importantly, it uses the forum style so looks like part of the site.
As I am an Administrator then I also have the ability to delete messages.
A minimum set of requirements are:
- It needs to be fully integrated into the forum so once logged in you can use the chat page without waiting for a 3rd party app' such as irc to load
- Admins and Mods should be able to delete messages
- Smilies and BB Code should be available, so people can post images, etc.
- Refresh time for active and idle should be configurable in the ACP
- There should be settings in the ACP to set the number of messages shown in the history and also be able to prune the table on a cron job