Literally any cheap knock off or disaster movie they're some of the best stuff. Go beyond Sharknado, people. Especially the shark ones. Sharktopus, Piranhaconda, Attack of the 2-Headed, 3-Headed and 5-Headed Shark, Atlantic Rim, Zombie Shark, Avalanche Shark, Exorcist Shark, Planet of the Sharks, Crystal Skull Apocalypse, Stonehenge Apocalypse, Stormageddon and so on. Some of the best quality trash.
Also almost any anime movie that sells itself as a new plot but is actually just a recap of the series plot with maybe a few new scenes and maybe some reanimation. Also Bonds Beyond Time.