Ben 10 Alien Force - Recalibrated Omnitrix

The Omnimatrix, better known as the Omnitrix, was a watch-like device that attached to Ben Tennyson's wrist in the beginning of the series, and is the device that the franchise revolves around. The device allowed whoever wore it to alter their DNA at will, and transform into dozens of different alien species, each with their own unique abilities.
The Omnitrix was destroyed in The Final Battle: Part 2.