Well, I know that floating grenades are a documented phenomenon. They've left a trail of blood commentary through Halo 1's history. For instance, bluedevil's T2T attempt from 2005 includes some floating grenades.

However, I was not familiar with how plasma/frags actually enter their floating positions. These shy creatures don't usually move on their own while people are watching, at least not enough that I've noticed.

Fascinating.