Flayed Mutants are undead specimens featured in The House of the Dead: Overkill Extended Cut exclusive to the level Creeping Flesh. They looks to be muscle bounded creatures similar to the Rage Mutants but with their muscles, flesh and intestines revealed.
The creatures were perhaps muscular butchers in their past human form. What makes them unique is that they have visible flesh, muscle, tendons and some bones. Their cranium can be seen.
Though these monsters look strong, they're actually weak from gunfire. Speculations believe that the reason they are weak is that the mutation only works on the necrosis of their cells but the revealing flesh doesn't add much protection. This could be the explaination why they are encased in meat refrigerators and why some couldn't walk.