Go to the level "The Covenant", Once you get past all of the enemies, look in the sky, you should see multiples hornets thousands of feet in the air, pull out your spartan-laser, and you can actually shhot them down! They'll come flying out of the sky, and into the water! It looks pretty cool, and I was amazed when I figured it out. I was pretending to shoot them as a joke, then all of a sudden the one I hit came flying out of the air. Then I did it to make sure it would work again.
P.S. This is pretty hard, and it takes VERY good aim to achieve this. Enjoy :)