Leopold is a Railway Gun in Kards - The WWII CCG.
The Leopold was a Krupp K5 gun (named Leopold by its crew), a railway gun used by Germany throughout WWII. With its 25 meter long barrel it had a maximum range of 64 km and it fired shells that weighted 243 kg. Two K5 guns, "Leopold" and "Robert", were shipped to Italy to help counter the American landing at the town of Anzio in 1944. The gun fired a few rounds but since it couldn't be evacuated due to its immense size during the German retreat, it was destroyed by its crew.