I just found out that the Bat signal is a heavy. Could I use it with Mr. Freeze gun?
Are there any other objects that can be used like this? like for example Tank turret with crimson gem.

any lantern can be classed as a light ...

Kryptonite too

It's still a special object though. Only one special object (ones with the gear symbol on their card) can be used per force.

That is incorrect, sir. One heavy (special or not), one light (special or not), one ANY (relic, immobile (Gamma Bomb), heavy, light, heavy special, light special, etc.). You can only have ONE relic or immobile.

Yeah - sorry, forgot rule #46,203