Voxel

Voxel is the original App Store 3D pixel editor! It's like Minecraft without all the mining. Use it to create simple sculptures, 3D icons, game-levels, or just to doodle with blocks.
Voxel is easy enough for kids to enjoy, but it is also designed for creative adults. Advanced users will appreciate Voxel's layering and advanced keyframe animation tools. Upload your models to the online gallery!

Simply tap in empty space to create the first block. From there you can attach new blocks to it by tapping any face. Or, toggle the grid guide to put blocks exactly where you want them. A color palette lets you change colors. Drag your finger on the selected block to rotate your view. Use a two-finger-swipe to rotate the view as well. Use the familiar two-finger pinch motion to zoom in or out -- or just hold your finger in one spot.

Now make models for use with Minecraft -- Voxel now imports/exports .binvox format!

Check out the stop motion made by printing 8 frames of a voxel animation:
http://www.flatblackfilms.com/Voxel