Price: £1.79 (HourFace), £0.59 (PhotoAvatar)
HourFace is simply one of the most disturbing apps I've ever tried. It recreates the instant aging scenes from Indiana Jones (either Temple or Crusade), turning photos of fresh-faced youngsters into wizened crones in seconds. Here's squeaky clean Robert Pattinson as he may look about the time the Twilight franchise finally fades into darkness in 2050.
The bar on the right lets you scroll through years in seconds, or simply invert your iPhone to reverse the process. The app works best on well-lit, full face photos - and try giving your phone a shake to activate a creepy extra.
PhotoAvatar is less likely to freak you out, unless you're susceptible to unconvincing transformations into potentially copyright-infringing monsters. The app basically cuts out your face and inserts it into one of three fantasy templates - one of which is suspiciously Cameron-eseque. Like HourFace, the avatars blink and move (slightly oddly) on their own, while wobbling the phone activates a special animation.
Both apps need a data connection to upload your photo and download the transformation - although the whole process only takes a few seconds. MotionPortrait is promising a zombie avatar app shortly.