Hearts of Iron
The grandest of Grand Vidya Gaem of Grand Strategy in Grand World War 2, made by the equally grand Paradox Interactive. Its contribution to /tg/ can be counted as: Expanding the Nazi Equipment page, inspiring Games Workshop and every little Tabletop gaming company about Dieselpunk, Mecha and Cold War ideas, and especially long nights of greasy, soda-drenched Axis and Allies sessions.
(To be filled in)