Hitler's Ark is the sixth and final mod released by Michael Collin. It features a heavily coded EXE that was based on registered Wolfenstein.
As such, most actors do not spill blood when shot at; they merely go to sleep. Some can still be killed with all the blood that it entails, though.
9 levels are featured. The EXE features e.g. textured floors and ceilings, animated corpses (guards sleep when they are shot), unique doors and 3D directional sprites.
It is only available in DOS.