Thanks for your reply, Thak!
If I were to try lightgun solutions on the Pi, I'd use a Wiimote + gunmod + this:
https://www.amazon.com/Mayflash-W010-Wireless-Sensor-DolphinBar/dp/B00HZWEB74
Then again... We might try House of the Dead 1 and 2, Daytona, Virtua On and many others via the emulation of their (lower quality) PC ports.