For me, PVC pipes (Carpet Python perches)
Paper towels/newspaper/butcher's paper/corrugated wrap...
Acurite thermometer/hygrometers
Ceramic Dog dishes
Pavers/bricks (to keep screen tops secured to glass tanks) and on that train of thought, I guess I could even say glass aquariums lol
I'm currently using 12 volt DC fans to increase ventilation in my PVC cages... those fans are designed for cooling DC brushless motor speed controllers (for industrial and robotic applications)