MetalGreymon

See? There's another rocket-shark! Metalgreymon isn't nearly as interesting as Skullgreymon, but it is the more accepted, more stable "perfect" stage of the Agumon line. In the west, this stage was known as "ultimate," but then Japan went and added a sixth stage of Digimon evolution they call the "ultimate" one, and the west was left calling that stage the "mega" stage. This is what you get when you make completely arbitrary dub changes, guys.

Another interesting thing about this one? In the original virtual pet, it had a blue-skinned, more sinister design and was said to have been corrupted by its attempt to evolve into a machine. It wasn't until the anime that they decided to make a somewhat healthier version, but they'd keep this one around anyway as a "virus" version.

...Did I neglect to mention so far that Digimon are sorted into three groups? "Viruses" are destructive, "vaccines" are more protective, and "data" are more neutral, though these categories do not necessarily indicate a Digimon's moral compass. There are plenty of villainous vaccines, heroic viruses, and more politically aware data monsters.

Digivolves from

 * 1) Greymon

Digivolves to

 * 1) WarGreymon