KhTZ-16
The Kharkov map is home to the KhTZ-16 Easter Egg. Once you destroy the Eastern-most section of the long building found at A3 you uncover a tractor-looking thing armed with a pea-shooter. This is because in Kharkiv, a tractor factory manufacturing the STZ-3 (yes, actually a tractor) was modifying them into KhTZ-16 tanks before the factory was evacuated and production moved to Stalingrad.
These vehicles were manned by two crewmen, and armed with a 45mm anti-tank gun, a 37mm anti-aircraft gun, and a 7.62mm LMG. So yes, pea shooters. 809 of these “tanks” were planned, but only 60 at the absolute maximum were actually made because they were bad.