Chris Brown & Rihanna 

flickr.com/SexyLexi78 

Rihanna and Chris Brown had people talking Sunday night, and not just because of their on-camera PDA at the Grammys.  When Rihanna took the stage to perform “Stay,” fans spotted a rock on her left finger that looked suspiciously like an engagement ring.  Twitter immediately lit up with speculation about her possible engagement. But while it’s no secret the couple is back on, they haven’t said anything about tying the knot.