Crayola,
When I said "issue" knives I meant the most common issue knives of the US military. These are often seen in surplus stores and gun shows here. The issue Army and Marine knife I have seen is the Kabar style with a long, straight double guard. The Air Force Pilot Survival Knife also has a long, straight double guard, and so does the Navy Mark "something" (I forget the number). I was aware that special forces groups get different knives.
I personally swore off knives without guards or inadequate guards after cutting myself with two different Becker knives. While holding them with the blades pointed up, the knives slipped from my grip and easily slid over my hand owing to the rounded, slick guards that are part of the plastic handles. I prefer straight guards because they are more likely to catch on one's hand than a rounded one, especially if the guard is short and slippery.
I have gone as far as to improvise my own guard on my Becker machette. I found a wall hanger that was made of a loop of metal with a screw in the center for mounting. I cut the screw off and bent the metal loop to make a guard I could slide over the blade, and then tied it on with wire and electical tape. You will never see an uglier guard, but IMO it looks better than blood gushing out of my finger.