"Is there anything else I should know?"
"Is there anything else you want to add?"

Adding one more sentence to state one more thing never hurts. But choose carefully because it is their last impression of you. If you felt you didn't show that much enthusiasm, here is your chance. Or if you feel that they didn't ask you about one of your strong traits, you have a chance to state it.

"I don't know if I expressed it that well, but I'm very excited about this position. I'm confident that I can do very well here."

"One final trait that I have that would be perfect for this position is my organizational skills. I'm very detailed and plan very well."