Just poked, shook and prodded my Titan, no rattle here Team Obi Juan.
Thanks for testing. I mostly notice when I sit it down on its back (inside a case), onto my cloth mouse pad. If I just tap the back side up near the camera on to the mousepad, there's something rattling. Can't determine where it's coming from.
The camera makes a bit of noise when in use, and I just tapped my Titan and it sounds similar to that. I don't know exactly what it would be in the camera, but I'm convinced that's where the noise is from. It's very subtle on my Titan though, so I barely notice it unless the room is silent.
I *think* I hear rattling when I tap near the top, but only when I tap. If I try to shake the phone, I don't hear anything.
It might be the camera, I think I remember on some other forum someone was complaining about something rattling in their iPhone 4S and they determined that it was something in the camera and that was normal.
Unless something on your phone is not working, I wouldn't be too worried about it.