2cute is a free, ad-supported app that lets you browse, download, and share images from the 2cute Web site--images that are empirically very cute (or as the app points out, in Japanese, "kawaii") of puppies, kittens, bunnies, and more. You can browse through large thumbnails of the pictures just by swiping left and right, and you can tap to rate, share, or download a normal or high-resolution version of the photo.
Flipping through the photos on 2cute is fun (with an occasional surprise, like a baby octopus or pygmy marmoset), and this app provides a great and easy source for getting cute, high-res pictures for your wallpaper. The app is still a little rough around the edges, though, and the photos that you tap through to can have inconsistent resolution and are accompanied by ugly metatext. That said, it's easy to download the pictures you want to save to your device, and then view them in your own albums.
If you like checking out new pics of cute critters--or you want an easy source of cute wallpaper--2cute is a handy little app.