With RealArtist you can add a smile to a photo and an even bigger smile to the person watching you do this.
Take a new photo or pick a photo from your photo library and nudge and tweak eyes, nose and lips and save your creations for later.
Zoom in for fine control over the regions to adjust.
Use the multitouch gesture pinch on the mouth to shut somebody up or try the gesture zoom to really open his eyes.