The ghost of a PDP-11
In the 1970s, the U.S. Navy and American Airlines used the PDP-11 from DEC to build the Multi-station Spatial Disorientation Device (MSDD). It was like a souped-up carnival ride that kept riders in the dark to simulate the disorientation felt in planes at night.
The MSDD was used until 2007, when it became too expensive to keep working. Migration Specialties moved the Navy to a modern machine which simulates a PDP-11 exactly. That FORTRAN code is still running on a PDP emulation card, which in turn emulates a fighter jet spinning out of control at night.
(You don't want to be the one who has to clean this thing