If you could only choose one piece of extra teaching equipment, what would it be?

Mine would have to be my visualiser. I love this device for many reasons:
☑️modelling virtually anything
☑️showcasing student excellence during a lesson
☑️exam technique practice
☑️recording demonstrations and processes
☑️live annotations and much more.

So, what piece of teaching equipment would you rather not do without?
#teaching #learning #teachers