An animal sniffing around your tent already knows you are there. I would not bolt up and scream, but I would not "play dead" either. Last summer we had a young black bear in camp. It was not yet next to the tent - instead it was checking out the bear cannister. A couple of sharp claps of my hands sent it off. Half an hour later it came back. Clapping and banging pots did not help. It was about 15 feet from the tent door. I got out, picked up trekking poles and cussed at it loudly swinging the poles. It ran off and did not return.

Bears, deer, elk, moose, marmots and other rodents - usually do not eat people, but they can ruin a tent. Mice are particulary bad at night. If I hear them, I run them off.