One-of-a-kind computer systems of which only one unit was ever produced (en.wikipedia.org)

Knew about ENIAC of course, but seeing MANIAC got a chuckle out of me.

Just read the page on the Deep Blue chess computers, was quite interesting.

The page on the Water Integrator is interesting.

Recall the NSA has a special line of computers - IBM Stretch and rumors of an x64 opcode just for them i.r.o crypto ???.

Missing from this list: the Foonly F1, used to create the animations in Tron (1982) and later to render the spaceship in Flight of the Navigator (1986) - of note as the first use of reflection mapping in a motion picture.

I highly recommend this video on the making of Flight of the Navigator. Apart from being highly entertaining, it also goes into stunning detail on all the special effects, in particular how exactly one goes about putting CGI into film in the 1980s (as the narrator points out - Final Cut Pro hadn't been invented yet!).

https://www.youtube.com/watch?v=tyixMpuGEL8

WW2-era ballistics charts were mostly done on one-off analog computers. A knowledgeable operator had to make adjustments daily.