Is there a reason why only act labs guns are suitable for MAME?.
How do lightguns have to work to be MAME compatable?
There are several lightguns around that "work" on a Pc (and Mame).
There are the older actlabs systems (GS I think they are called), the actlabs TV gun, actlabs VGA gun, the 'PC Super Bio Gun' and the 'PC Virtual Gun'. All work in mame, but the problem is accuracy - PC guns are notoriously compared to console guns. Some are reviewed here:
http://www.retroblast.com/hardware.htmlTo cut to the chase, Act-labs are currently the best (un)available gun for a PC.
Console guns DO NOT work on a PC. No console->PC adapter makes them work either (apart from the trigger button).
NB Other future options: (you could be waiting a LONG time)
Happs re-sell an interface that lets you use standard arcade optical guns on a PC. This actually looks pretty good, costs $160 - but no one has tried it at all. It looks like there are some issues that would involve someone coding a driver for it perhaps - there was interest but I have not heard anything for a while.
A company called
http://www.erealgames.com/ make a lightgun based on a camera mounted on top of your camera. This has potentially HUGE advantages over all the above guns, as they do not mess with the video of the system at all - no white-blanking of the screen on every shot.
It is not avaiable for the PC although a guy from the company posted on these boards saying they were looking into making a PC version.
Another option is a conversion/copy of the 'Gun Sense' system used on more recent Sega arcade games (Lost World, Vcop3, HOTD3 I think). This basically sticks 10 infra-red LEDs around the monitor, and has a detector in the tip of the gun. It works extremely well - its basically a pro version of the erealgames 1camera option. Ultimarc - makers of Ipac/Optipac - plan to look at this idea. The catch is that they will basically be designing it from scratch.