This brute idea actually came about when i was brainstorming neat ideas for those big mars monster guys in the upcoming game Destiny. "brutes"What i was thinking was that at any random moment in a wide open area a pack of gravity hammer brutes would blow up out of the ground and fly in the sky. When they reach the ground again the wack! the gravity hammer making a super-powered line blast on the ground(kind of cracking the ground and making dust so you can see the attack coming at you. I was also thinking you could implement this in matchmaking where you can fall from a high place and do this attack or use a jetpack to set it up easier!
Flood firefight is self explanatory!!!
I was also thinking that with this idea that the higher you fall from the stronger the attack and the attack uses twice the normal ammo of a regular attack and "somewhat" difficult to avoid(adding that extra level of difficulty in campaign!) A great counter would be jet pack, thruster pack, and hardlight shield(you take a little damage though). Seriously though, how often do you see someone use up their entire gravity hammer before they die- 20%/ 10%? i dont think the ammo requirement for the attack is an issue.