SkullGreymon

A mutant digivolution of a Greymon that has been raised in the wrong way. His name comes from the English word skull, with grey being a misspelling of great.

SkullGreymon has a body composed of bone. It has no feeling, and fights only with its instinct.

Digimon Adventure
SkullGreymon is an alternate Ultimate for Agumon that appears once.

Digimon Adventure 02
When the Digimon Emperor took over Greymon with a Dark Ring, he wanted him to Digivolve into MetalGreymon but he instead turned into SkullGreymon again and defeated Meramon, Flamedramon, Halsemon, Digmon and a bunch of DarkTyrannomon before reverting to Agumon as the Digimon Emperor made off with him. No matter how much he tried to get Greymon to Digivolve to MetalGreymon, he turned into SkullGreymon until Agumon's recapture and the introduction of the Dark Spiral turned Agumon into a Virus version of MetalGreymon.

Digimon Tamers
A SkullGreymon was among the many Digimon seen through the rip in the sky during Vikaralamon's rampage.

Digimon Virtual Pet
A glitch in the Digimon virtual pet system allowed a person to receive an Ultimate-level powered Digimon that looked somewhat similar to Greymon, but appeared very glitched. It was dubbed "SkullGreymon." It was not an official release of SkullGreymon, nor was it called that by anyone in Bandai, but it was the first time anyone had ever used the name in America to describe any Digimon.

SkullGreymon did, however, appear in the second version of the Digimon Battle Pet.

Digimon World
SkullGreymon lived in the basement in Dark Mansion. After being beaten he joined the Colosseum.

Digimon World 2
greymon can digivolve into skullgreymon if it have 20 DP and can digivolve further into Machinedramon.

Digimon World 3
By increasing Agumon's dark resistance, one can unlock his SkullGreymon digivolution. For partners other than Agumon, SkullGreymon is unlocked by Greymon, and can unlock BlackWarGreymon.

Digimon World 4
SkullGreymon is the first boss you will encounter in Dry Land.

Digimon Digital Card Battle
SkullGreymon belongs to the Dark card group and has HP 1700, circle attack 960, triangle attack 350 and anti-Nature cross attack 450.

Digimon World DS
SkullGreymon appears as a boss in the Chrome Mine when you are trying to rescue Phil. At first, he appears as a Machinedramon. Phil tricks him into inserting a chip that degenerated him into SkullGreymon instead of digivolving him. He takes up three spaces in battle and is level 21 with an extremely large health bar.

Digimon World Dawn/Dusk
SkullGreymon digivolves from DarkTyrannomon and can further evolve into Machinedramon.

Attacks 
 * Dark Shot (Ground Zero): Fires the fish missile on his back.
 * Double Dark Shot (Ground Zero Modified): Fires 2 fish missiles.
 * Curse Breath: A purple breath that paralyzes the enemies.