I've talked with some other ppl about the whole US Dreamcast gun thing before. Many times 3rd party controllers/etc. are not allowed to have "official" logos/etc. on the items. They can be made "for" a console, but just can't carry the "official" logo.
With that being the norm, there is a bit of a question as to Dreamcast light guns. Out of every Dreamcast light gun I have seen/used, there is only ONE that carries the "official" US orange Dreamcast swirl logo. That gun is the MadCatz light gun.
The prevailing "theory" is that MadCatz was going to be producing the "official" light guns for the Dreamcast until Columbine occured. At that time, Sega decided it was better to not release an officially licensed light gun. So, what was MadCatz to do with all those guns that already had the "official" logo on em? Well, repackage and ship those puppies out as a 3rd party controller.
So, the closest you could get to an "official" US Dreamcast light gun would probably be the MadCatz version.
I've tried out 4 different guns on the DC. The Starfire light blaster is my favorite (even thou the triggers break WAY to easily on them due to poor quality engineering). I've fix the triggers on ours so they don't break any more. The Pelican light gun is my next favorite. The trigger seems a bit "light" on the gun to me thou. The MadCatz gun is okay, but the feel of the gun (size wise) just didn't feel right to me. The Yobo brand light gun is the last one I've used and my least favorite (it was junky). I think the Yobo gun is the same style that was officially release in Japan/Europe.
Anywho, hope some of this helps, or, at the least, is informative...lol.