Sentinel beam/Gameplay

Campaign

On the Halo 2's campaign level Quarantine Zone, provide two of the player's Sangheili allies with Sentinel beams, and have them board the riding seats of one's Type-46 Spectre. Since NPCs can't run out of ammo, they make excellent weaponry. Unfortunately, further in the mission, if one manages to keep both Sangheili and Spectre intact to that point, one must leave the Spectre.
In Halo 3, the Sentinel beam performs greatly against the Flood, as Infection Forms will burst if they are even slightly touched by the beam. Human Flood combat forms will die instantly, though Elite and Brute forms may take longer to kill. Aim for the Infection Form embedded in their chest and one will kill it. Pure forms are tougher due to their evolved forms; Stalker forms and Ranged Forms will die by the time the weapon overheats whereas the Tank Forms will require two long blasts to take down from the stomach.
In Halo 3, the Sentinel beam is very useful for taking down a Brute's power armor quickly and effectively. It is also great for taking down Jackals and their shields, as well as Grunts' armor, though it may overheat after prolonged firing.

The Sentinel beam is quite rare in multiplayer games, and if available, it can be a powerful weapon in the hands of the well-trained.

This is best used in a small map like Warlock. Also good for Headlong as long as one has other more powerful weapons.
If the Sentinel beam is the only weapon you have, conserve ammo and rely on meleeing as much as possible. It has a quick and effective melee. Only fire the weapon when your target is far away, because ammo goes fast. Melee in close quarters, and avoid deadly crossfire. Replace it as often as possible.
A Sentinel beam is useful against unshielded foes, so use a grenade to take down the opponent's shields followed by a burst from the Sentinel beam can quickly kill an opponent.

During a game of Infection, the Sentinel beam is an effective way to rid yourself of chasing Zombie forces, but take care as to where you aim, since the beam is easy to spot and is likely to give your position away if the shot goes astray.
When loading up vehicles, a Sentinel beam in the passenger seat is an incredibly deadly tool. The most flexible location is in the back seat of a "Mongoose", although the passenger seat of a "Warthog" or "Prowler" is also useful and advantageous to the match. The advantage of vehicle-bound Sentinel beams is that it can 'clothesline' foes (although this technique should not be depended on).
Steady shots can make the Sentinel beam a great anti-sniper weapon. Fire at the sniper and then sweep the area. You will eventually meet your target, and they will have a difficult time evading the beam. While this technique is unlikely to kill a competent sniper, it is a good way to prevent them from using their scope.
The Sentinel beam has an extremely large power consumption rate, about 5% per second, so always carry a backup weapon and try to save the Beam for emergencies.

The new Safeguard Sentinel Beam variant operates similarly to its previous breathren, with the addition of a smart scope feature. The addition of the scope extends the weapon's effective range quite a bit.
Still effective against infantry in the open, even sprinting targets.
It can be surprisingly effective against enemy vehicles, doubling as a impromptu Spartan Laser in Warzone or on the few maps that it spawns on. Adding a Damage Boost to it can melt something as large as a Wraith in seconds.