I've been out of it for a while now, but I spent a number of years Nerfsmithing. Which is to say, I modified Nerf blasters. I upgraded the internals to get longer range and higher rates of fire. My real fun, though, was modifying the exteriors to see just how silly I could get. I made a lot of different designs, but below is my masterpiece.

I attached a real red dot sight, after carefully painting it to look like a Nerf accessory. I attached a real laser sight and tactical light, after mounting them inside the case of what had been an official Nerf light. The 10-round straight magazine was replaced with a 35-round drum magazine. A rifle strap (in bright yellow) and a Nerf bipod finished off the main unit (a Nerf Stampede).

Then I attached a Nerf Magnus pistol, still fully functional, as a front grip. And I attached a Nerf Zombie Strike Machete under that as a bayonet.

It looks overbuilt and ridiculous, which is what I was trying for, but it was also an absolute terror in the office Nerf wars. I had a lot of fun building it.