I loved lightgun games on the old systems, and I think the Sega Saturn’s Stunner was the best hardware of the lot. The obsolescence of CRTs pretty much killed the tech, but the gameplay style has made a bit of a resurgence a couple times with the advent of the Wii and VR.
I’ll throw out another one, too: force feedback joysticks were amazing for flight sims, but I’m not sure you can get a new one at a reasonable price (and I don’t think the software side supports it either).