Quantum stealth
If you thought camouflage was hard to see, imagine a technology that actually bends light waves around a soldier's uniform, making them seem invisible. That's the idea behind quantum stealth, a technology still in development.
The pictures currently shown are pretty mind-boggling, with people blending into multiple types of backgrounds, but they are still "mock-ups," so it's not clear exactly how well the technology will work when it's put on the battlefield
Gyrojet carbine
Why shoot at enemies with regular old air-propelled projectiles when you can use rocket fuel instead?
That was the premise behind the gyrojet carbine, which made its debut in the 1960s. Instead of regular pressurized gas, which his what ordinary projectile firing devices use, the gyrojet could be made lighter because it didn't require compressor cartridges for pressurizing gas, according to Forgottenweapons.com. Instead, the gyrojet would launch rockets that burned their fuel as they traveled down the barrel, meaning they were actually at their fastest once they had left the barrel, according to forgottenweapons.com
However, the guns were woefully inaccurate, and very few of them got made before the makers, MB Associates, went out of business.