The Cacodemon from Doom is an oddly shaped circular beast that doesn't seem like it would lend itself to Legos, but Bart De Dobbelaer went for it anyway.

In Doom 2's instruction booklet, this is how the Cacodemon is described: "They float in the air, belch ball-lightning, and boast one Hell of a big mouth. You're toast if you get too close to these monstrosities." This one looks a little more friendly, but still intimidating.

[via The Brothers Brick]