Halo 2 > Halo 3 > Halo 3 ODST > Halo Reach > Halo CE
Based on campaigns.
I found a way to fet a groupd of ALMOST unbeatable elites and grunts. Thuderstorm skull would make it about 10 times more effective as well.
When tou get to the brute weapons cache, clear the area of enemies, and wait for a group of 4-6 elies and two grunts to form. You may have to do a bit of prompting to get some of them to move, and escorting a grunt through the doors on the way may be required.
Once formed, there are multiple combinarions of weapons you can give them. I did this
Gave a zealot and two spec ops a shotgun
Two spec ops brute shots
A grunt a rocket launcher and the other grunt a fuel rod
This combinarion tore apart the oncoming brutes and jackals.
I also tried this
Zealot=shotgun
Spec ops x 2=brute shot
One spec ops a shotgun
One spec ops a beam rifle
Grunts with fuel rod and rocket
That worked well.
Also giving ALL the elites brute shots is very effective.
Do NOT give a rocket launcher to any of the elites. I guarantee it will get beaten to death by the brutes. Grunts keep their distance anyways, so they do fine.
So there are some combos to try for your mini army, also try out some of your own. The only annoying thing is, in the tunnel the grunts may lose their rockets and fuel rods from diving from the ghosts, so you will have to give them back to them. Apart from that, they should tear everything apart