At one time, a fan transferred maps from DOOM to Minecraft. Now, another enthusiast has created a mod called Voxel Violence that adds sandbox-style blocks and a building system to the popular shooter.
A new mod for DOOM 2 allows you to build different structures, as well as undermine them using TNT blocks. At the same time, so far the appearance of the blocks copies that of Minecraft. But otherwise, it looks pretty good.
You can download the Mod here.