First conceived as a heavy tank during the later stages of World War II, the M26 Pershing saw service near the end of the war in Europe, destroying just 7 German tanks. It later served in the Korean War alongside M4A3 'Easy Eight' Shermans, fighting off T-34/85s and emerging on the winning side.
Although its military career was short lived, if it weren't for this vehicle, the M46 Patton, as well as the subsequent M47, M48 or M60 Patton wouldn't even exist...
This tag implicates tank (learn more).