In Halo 2, when facing multiple foes, Dual-Wielding two Brute Plasma Rifles can be a key tactic, especially on Legendary difficulty, as using two will result in a storm of plasma bolts that can cut down enemy formations quickly. This can also help when facing the Flood. The downside to this is that the rifles will overheat fairly quickly, leaving the player vulnerable to open fire.
A way to overcome the fast overheating issue is to fire one rifle until it overheats and then the other. Firing both in bursts can also prevent overheating.
Dual-wielding the Brute Plasma Rifle with a standard Plasma Rifle is another good tactic. The Brute Plasma Rifle will overheat faster and by the time the Elite Plasma Rifle has overheated, the Brute Plasma Rifle will be ready to fire again. This can be useful when facing large quantities of Flood. Note however, that this tactic will drain a lot of power in a small amount of time, and replacements are a necessity.
Both Plasma Rifles strip shields better than damaging flesh and armor (and thus, are not as good at eliminating the Halo 2 Brutes as, say, the Battle Rifle), their true value lies in their rate of fire and their ability to stun opponents. In ODST, this ability to take down shields is even more effective, as they can remove a Brute's Energy Shields in a matter of seconds. The brute plasma rifle is also effective against swarms of Drones.
A third tactic is to dual wield a Brute Plasma Rifle and a human SMG. This is one of the most powerful combos and can defeat even an Energy Sword wielder. The only disadvantage is that it only works at mid-range, and you need some very good aim because if you fail to aim properly, you may be left with an overheated Plasma Rifle and an empty SMG. In order to combat the lack of SMGs in levels with the Brute Plasma Rifle, try dual wielding a Needler with it as well, as these weapons are normally in huge supply on such levels. Also with this way a good aim isn't a necessity as the needles home in on enemies and damage them this means it is more useful for those that can't aim as well so they can remove enemies shields then kill them with the least amount of ammo needed.