The Type 4 20 cm Rocket Mortar and the 20 cm Naval Rocket Launcher. The first one has a 203 mm caliber. The second one has a 210 mm caliber. These could be quite unique to set up and fire as well. As opposed to the AT launchers that we are used to in-game.
Source: Type 4 20 cm rocket launcher - Wikipedia
20 cm naval rocket launcher - Wikipedia