Shoutbox

It shouldn't cause conflicts with Plus! (in fact some features even need Plus to work!) but judging by it's track record you'll most likely have personal conflicts with it (I know I and many others have)

It's quite possibly the most buggy add-on that's survived year after year that I've ever used, still you're welcome to give it a go. I'm sure all the nasty nasty bugs have been squished by now