When Apple introduced the iPhone 2 to the market, it was with Photo Booth, a fun app that allows you some time on the Mac could create distortions in your face. The dual-core processor and front camera for making the iPad 2 Photo Booth. Still got the iPhone 4S, with the same processor and a much better camera, no pre-installed version of Photo Booth. @ appled3v iOS hacker has managed to change that, if there is no release to the general public is appropriate. The app only works with the front camera on the iPhone 4S, but there will later support the camera on the back of the unit. Also the number of effects is still limited, there are now only four, but the plan is to extend this to all effects.
If Photo Booth ever becomes available, you have a jailbreak for that.