Somewhat related: In my NES hacking to PCE fever, I was gonna hack some lightgun games for NES/Famicom to PCE. Rigging up the NES gun for the PCE controller port is a cinch too. Never got around to it (didn't think there would be much appeal for this either).
On a side note; for the PCE to have a "real" lightgun system and not what the famicom/nes did, you need to have a counter inside the gun (two 8bit ones actually, one for the scanline number and one for the horizontal pixel equiv) and you reset this counter on vblank interrupt. When you gun sees the edge of the horizontal beem like in arcade, genesis, snes setups - the counter value is stored to a register. On vblank interrupt, you read that value from the port (and reset the gun so it's resynced to the TV). Pretty simple stuff (and very cheap to do), but PCE *did* lack this small feature on the internal side. So that small part has to be external. Definitely not a big deal though. And like others, I'm really surprised this wasn't made.
The method I just described allows you to point to the screen (without pulling a trigger) and have a cursor/target/pointer updated in realtime. The famicom/nes method is not like this. When you pull the trigger, it turns everything black and leaves only the target white. If you have more than one target, it has to flash the screen a few times like this and cycle through. So it's really only good for 1-2 objects. The more objects you have, the longer the flashing is. Kinda limiting for some projects.
