Keera Sound Delay replays whatever you say... with a small delay. Plug the headphones, give it to a friend and see how funny they sound when they try to talk.

Note: You need headphones to use this app (otherwise, the sound feeds back into the mic and you'll only hear a very annoying loud noise). The new version addresses an issue with some phones, let us know if headphones are still not detected in yours (please, include make and model, so that we can try it with something similar).