The heliostat, the heliotrope, the helioscope. Early 20th Century electric searchlight spectacles. Medieval and renaissance magic-glass conjuring. Riviere's Theatre d'Ombres. The Talking View-Master.
Dead thrill rides.
Defunct digital VR systems. The Indecks Information Retrieval System, Diebold Cardineer rotary files, etc. Yamaha CX5M etc. etc. etc. Dead computer languages. Dead Internet techniques.