My cheap pneumatic nail gun came in a card board box. Once it was fitted with a quick disconnect for it's air connection, it became an ill-fitting card board box.
The new wood box has plenty of room for it and a supply of nails. This box is the biggest I've made so far. It's made from half inch plywood. The handle was salvaged off of something in the recycling bin at work.
I think the box needs a little sub-divided section to keep the nails from sliding around...