Although I do not need guns to have a good game, having them, done good, would not be bad either.
However, if any gun is ever added, something I doubt, I would advice only fantasy steamtech.
Fantasy Steamtech is like the things you find in games such as Warhammer: Steam Cannons, Tar Guns, Heavy Ballistas powered by steam, etc.
Steamtech (a more medieval version of Steampunk) can make a game very interesting. But it also can ruin it, specially when you are trying to get a magical based medieval mithology.
Steamtech, if used, should be extremely rare. Dwarves would be the most logical groupd to have these tipes of advances, and even there it should be rare.
Note: Machines do not specifically mean advanced technology. Several machines where avaliable during the medieval times. And, since this is fantasy, you can tweak that a little. Add baloons, flying machines and the such, but do not add submarines and electric weapons (electric weapons where a mistake made in Dungeon Siege, where they definitely didn\'t fit).