Z-4190 bubble shield/Gameplay
From Halopedia, the Halo wiki
When fighting large numbers of Covenant forces, the bubble shield is useful as it protects you from all sides. However, certain berserking Brutes may leap inside the shield and beat you down. It is particularly useful against Drones, partially because they usually surround you, and partially because they rarely attempt to enter the sphere. Be aware, however, that after approximately 20 seconds, the shield will deactivate, leaving you wide open to attack.
Another situation in which the bubble shield is useful is protecting you from a Scarab detonation. It will stop the explosion from harming you completely, unless the explosion starts on the inside of the bubble shield. As such, it is advised that you at least exit the Scarab before using the bubble shield. Beware that the Scarab's debris will fall through the bubble shield and may end your moment of victory prematurely. Another strategy is to use a bubble shield as a stepping stone, breaking up combat and allowing the player to use the bubble shield to block enemy fire while retreating. This is especially useful at the end of The Storm, where there are large, linear sections.
A good tactic when enemy troops deploy a bubble shield is to "take over" their bubble shield. Charging into a bubble shield often catches Covenant troops off guard, and enemies wielding heavy weapons such as Fuel Rod Guns or Brute Shots will not fire at such close range. Bubble shielded enemies can easily be overpowered by melee or close-ranged weapons as their teammates look on helplessly outside. Keep in mind that the Flood will usually just charge right in, so it is not much use against Flood forms other than the Ranged form.
The bubble shield is an incredibly useful piece of equipment in any Multiplayer game or match. These are a few yet vital tactics that you should know if you want to use the bubble shield to its full potential. If you have been in a close range fight with another player and your shields are down, it is often a good idea to use a bubble shield to give your shields time to recharge. Also, if you have a Shotgun, Energy Sword, or a Gravity Hammer as your secondary weapon, and a player with a regular weapon (i.e. Assault Rifle or Battle Rifle) is running to you, drop the shield so that they will be forced to come through the shield to finish you off. Right before the player gets to the shield, pull out your Sword/Shotgun/Hammer and surprise them when they step through. If you do not have a close range weapon, use this same strategy except with a Frag or Spike Grenade. Time the grenade so that it will explode right as they step through while you step out the other side of the shield to avoid damage. If done correctly, the grenade will deplete the enemy's shields so you can kill them with a single melee hit or headshot.
Many players often deploy their shield and taunt their opponent by teabagging or simply doing a "staring contest". This can call for some embarrassing moments, as another player can easily flank and assassinate them.
Another method that is very useful is the Man Cannon - bubble shield combo. In Valhalla and Narrows, campers often take position so that they can easily open fire at players landing from the Man Cannon. A player can use the bubble shield by sending it first into the Man Cannon, thereby securing a safe landing zone on the other end of the Man Cannon, protected from enemy fire and grenades. Also, smart players can activate the bubble shield as they enter the Man Cannon, effectively giving them cover as they fly through the air. This tactic is useful if the deployer is holding a flag or oddball.
A way of getting through an opponent's bubble shield is to get a vehicle and drive into the player hiding in the shield. This works particularly well with a Warthog or Ghost. Another strategy is to rush towards the shield and step back right when you're in front of it. If done correctly, the other player will overreact and step out of the shield, giving you an open shot.
Another strategy is to catch an opponent using heavy weapons by surprise by throwing a bubble shield in front of them as they fire. This calls for precise timing and close quarters. To pull this one off, a player must be within a reasonably close distance to the enemy and must deploy their bubble shield almost exactly as the enemy weapon is fired. The activating bubble shield will cause the shot to explode in their face, often causing a suicide or giving the bubble shield deployer the kill.
A similar situation can occur with plasma grenades. Activating a bubble shield as an opponent tosses a plasma grenade towards you can cause the grenade to bounce off the bubble shield and stick the player who originally tossed the grenade. The travel distance of this bounce is not far, so unless your opponent is charging into the bubble shield this does not happen often.
One anti-personnel combo calls for a bubble shield and a spike grenade. If someone deploys a bubble shield as protection, then another person can walk into the shield and throw the spike grenade at the inside of the shield. When the grenade goes off, the bubble shield will keep the spikes inside, and anyone unlucky enough to be caught inside the shield, unless they are on the opposite side, will be shredded by the ricocheting spikes. You can also activate the shield then use active camouflage, as the shields hides the ripples created by the invisibility.