Morph Ball Bomb
A Morph Ball Bomb is a small, time-detonated explosive that Samus can deploy while in Morph Ball form. It can be used to damage enemies, as well as execute the Bomb Jump and related techniques. The bombs can also be used to destroy materials otherwise impervious to Samus's weaponry, such as Sandstone and Talloric Alloy. The supply of bombs is unlimited, though some appearances have a "cool down" period which only allows Samus to drop three bombs at a time. She regains the ability to drop one of these bombs about a second after an already laid bomb has been detonated.
The Bombs can also be used to propel Samus in the air, about twice the height of her Morph Ball. Bombs dropped in the air are noticeably not affected by gravity. This attribute can help Samus - in the Prime series, a difficult but necessary technique called the Double Bomb Jump can be performed, and in the 2-D games, the jump is very useful for sequence breaking through a technique known as Infinite Bomb Jump.
The Bombs are also key in fighting Metroids, as they can knock the predators off Samus if at least one manages to latch onto her.
The Bombs are located within Brinstar, at the bottom far-right of the area. The Chozo Statue holding it, however, is blocked off by a Red Door that Samus can only open with Missiles. Once she obtains it, she can drop bombs to attack foes like Zoomers, propel herself upwards and blast open passageways. This last ability makes the upgrade essential as it is the only way to access the hideouts of Kraid and Ridley. A programming quirk can let Samus jump off a bomb explosion as if it were solid ground, which can aid in certain sequence breaks.
Metroid: Zero Mission
As with the original game, the Bombs are located in Brinstar, within the same general area. As before, Missiles are needed to open the Red Door and gain access to them. While they still damage foes and blow up Bomb Blocks, the explosion happens much faster than in the original, making it easier to use for bomb jumping. The tool is also required to activate Morph Ball launchers in Kraid and Norfair.
Samus possesses the Morph Ball Bomb while traversing the Frigate Orpheon, but subsequently loses it after an explosion cripples her Power Suit. It is only by traversing the Chozo Ruins on Tallon IV and destroying the Incinerator Drone that she reaquires it. The bombs can damage foes, destroy sandstone and Talloric alloy structures, and activate Bomb Slots to operate machinery. It is also a vital weapon against Flaahgra, doing immense damage to the beast. However, only three bombs can be dropped at a time, and must be recharged before more can be dropped.
Metroid Prime Hunters
The Bombs are part of Samus's default abilities, and function exactly as they do in the rest of the Prime series - up to three can be dropped at a time, and they may destroy obstructions in Morph Ball corridors.
Metroid Prime 2: Echoes
While having the Bombs upon landing on Aether, Samus soon loses them to the Ing after entering Dark Aether. The Ing that stole the Bombs from her soon possesses the Alpha Sandigger in the Agon Temple, transforming it into the Bomb Guardian and granting it the ability to use bombs exactly like Samus could. After destroying it, Samus reaquires the upgrade. As before, the bombs are used to activate Bomb Slots, damage foes and destroy Talloric Alloy structures. The bombs are also vital against foes such as Amorbis, the Spider Guardian and Quadraxis.
Metroid Prime 3: Corruption
The Bombs are part of Samus's arsenal from the beginning, and at no point is she forced to reobtain them. As before, damaging foes, performing Bomb Jumps, operating Bomb Slots, and destroying Talloric alloy obstructions are the main uses of the upgrade.
Metroid II: Return of Samus
While exploring SR388, Samus finds the Bombs in the hands of a Chozo Statue in some ancient ruins, with the only obstruction to it being a Red Door. With the Bombs, she can destroy certain blocks and open up passageways. However, care must be taken if using it on the ceiling, since an explosion will knock Samus out of the Spider Ball state. The Queen Metroid is also susceptible to Bombs if Samus lets the Queen eat her while in her Morph Ball, then rolls into her stomach and drops several bombs.
Shortly after landing on Zebes, Samus can find the Bombs in Crateria, but after getting them she is pitted against a Torizo. Afterwards, she is able to use them to blow up obstructions such as Bomb Blocks and perform Bomb Jumps. With timing, she can even perform an Infinite Bomb Jump to reach places without needing certain upgrades. With the Charge Beam, she can also perform the Five-Bomb Drop, a technique that lets her drop five bombs at once when going into the Morph Ball. Unlike normal bombs, however, bombs dropped via this method are affected by gravity, and explode slightly later.
Metroid: Other M
Although Samus has the Bombs from the start, she is not authorized to use them until after the Brug Mass has been defeated. With them, she can operate Morph Ball launchers, destroy certain obstructions, damage foes, and perform Bomb Jumps (though they give less height compared to the Spring Ball). She is also able to use the Five-Bomb Drop again, in almost exactly the same way as before.
As a consequence of X Parasite infected Power Suit pieces being surgically removed, Samus loses the ability to use Morph Ball Bombs, and must download data for the upgrade from a Data Room in Sector 2 (TRO). With it, she can blow open bockages in passageways and destroy Bomb Blocks. The bombs, however, take a lot longer to detonate than before, making Bomb Jumping with more than one bomb impossible.
Super Smash Bros. series
In all four games in the Super Smash Bros. series, the Bombs function as Samus's Down Special move. With it, she turns into her Morph Ball, drops a bomb, then unmorphs. The dropped bomb falls a short distance (bouncing if it lands on the ground) before exploding, damaging anyone unlucky enough to be caught nearby. If Samus is near a bomb when it explodes, she'll go into her Morph Ball state and bounce up a short distance. This, similar to infinite bomb jumping in the Metroid games, can be useful in a skilled player's hands to increase horizontal recovery.
Super Smash Bros. for Wii U and Super Smash Bros. for Nintendo 3DS both eature unlockable variants of the Bomb - the Slip Bomb, which deals little damage but causes opponents to trip and can perform meteor smashes in the air, and the Mega Bomb, which is stronger, but takes longer to detonate and of which only one can be used at a time.