Scorpion rocket launcher. (This one is legitimately neat. YES, the designers know what backblast is, and the design redirects it to the side and away from the shooter. NO, the launcher is not permanently attached to the M16, it fixes using the bayonet lug and goes on and off just as quickly.)
Do the Shuttle Carrier Aircraft count? The space shuttle is an aircraft with the flight characteristics of a svelte brick. It'll land just fine. It only lifted off in Cowboy Bebop. So to fly it from place to place, without taking the long way up, it'd piggy-back atop secondhand 747s. They didn't bother replacing the American Airlines livery for at least five years.
The mounts on top read "attach orbiter here - black side down."
I made in my teens a gun from Lego Technic that shot a lady cracker with another lady cracker. It got about 20 m before the cracker exploded after 0.5 seconds.
Sadly no foto, and it got unusable after about 20 shots.