JuxtaposerCurrent Version: 2.7.2

Juxtaposer lets you combine multiple pictures into fun photomontages quickly and easily thanks to its amazingly intuitive and responsive user interface.

Take any element from one picture and add it to another. Put your friend's head on a statue's body, remix your pets into a mythical creature, or magically join your favorite band, it's simple and the process is fun.

Quotes from external reviews:
* TUAW: "This $2.99 app is a lot of fun, as well as one of the best-executed compositing tools for a mobile device that I've ever seen."
* IphoneAppReviews: "Pretty much everyone, at some point in time, has had the uncontrollable urge to take a friend’s photo and do something truly evil with it. Juxtaposer is an awesome photo-editing tool that can make that dream a reality!"
* WhatsOnIphone.com: "The application works incredibly well and makes an otherwise challenging process simple and fun. It blows my mind that you can do such things on an iPhone."

This is how you work with Juxtaposer: First, load in any two pictures - perhaps one of your dad, and one of your dog. Next, use your finger to erase around your dog's head.
Quickly zoom in and out using two finger gestures. To cut out your dog's head exactly, you first zoom out and make a rough outline, then zoom in, and erase or un-erase with pixel-accuracy.
Switch to move mode and use two fingers to move, re-size and rotate your dog's head into place over dad's.
It's easy, intuitive and fun, and you'll have a great new Dog-Dad in about a minute.

There is detailed in-program help if you need it and many cool features, including:
- Unlimited undo means no mistake or accidental brushstroke is permanent.
- Save directly to your photo album.
- Save multiple sessions and return to them later.
- Save top image cutouts as 'stamps' and use them in future projects.
- Share your edited image on Facebook, Flickr and Twitter.
- Use hard or soft brushes to create sharp or blurred edges.
- Create smooth blends between images with transparent brushes.
- Keep adding elements from other pictures to your composite image if you like.
- Red mask mode (second screen shot) lets you accurately isolate part of one image without being distracted by the second image in the background.
- Translucent mode makes it easy to align your images precisely.
- The stamp tool lets you add multiple copies of your cut-out to your composite.
- Work in portrait or landscape orientation; optionally have images auto-rotate.
- Supports output resolutions of up to 2048 pixels on iPhone 4, iPhone 3GS and current iPod Touch; up to 1024 pixels on older devices.
- Switch to and from full-screen with the tap of a finger.
- Double-tap to quickly switch between erase and un-erase functions.
- Flip the top image.