I have a pair of GunCons (Scorpion 3) working perfectly at 640x480 resolution on a Wells Gardner D9200.
There are working as well or better than the Actlabs (which I also own), AND I can use two of them.
I'm using Smog's driver, and a home built circuit that provides +5 and +9 power to the guns and uses Andy Warne's jpac small chip to get the composite sync from the VGA signal.
If you can build a simple circuit on breadboard, this is a GREAT option.
There are several threads about getting the GunCons working on a PC and a PC monitor in these forums.