I have some toy guns that look alright for photos.
A compact SMG that looks good and suits cosplayers of any size. It has a shoulder stock and iron sights, and looks great in photos.
The AUG is a larger assault rifle with a distinctive shape that stands out. This model is big and comfortable to use, but looks fairly plastic-y.
The P90 is a compact personal defence weapon, similar to an SMG. It has a very distinctive and recognisable shape. This one has a non-removable suppressor on the front making it longer than normal. It is a little uncomfortable to hold properly due to the hard plastics and weird ergonomics, but the size is good for most cosplayers. This one looks a little bit plastic-y.
One of the most widely used pistols in the world, it is easily recognisable and suitable for cosplays that don't need a specific type of pistol. This model is very well made and has a functional slide, hammer, and magazine loading mechanism. The M9 is a full-sized pistol, so this model will probably look a bit big in most cosplayers' hands (it's a tiny bit too big for my hands to hold perfectly comfortably).