I am going to include one link and an image. Here's an M16A1 outfitted with a grenade launcher and a Starlight scope. The Air Force set this up in 1967 creating an eighteen pound weapon out of an eight pound rifle.
There is no end to the obscurity. Pinfire harmonica pistols? Early efforts at semi-auto military rifles? How about a Remington Model 8 shotgun with a 15 round box magazine? If you don't see that last one, you haven't wandered back far enough through the older posts. I'm tempted to just find the oldest page and read forward.