As an item
Upon spawning, Bob-ombs can be picked up by any character and subsequently thrown at opponents; owing to being an explosive, the item can easily inflict considerable damage and knockback against other players, though its splash damage can also potentially harm the attacker. However, holding onto the Bob-omb for too long can cause it to automatically explode in the user's hands, and getting attacked can potentially cause the item to go off as well; if the Bob-omb begins flashing red while it is being held, it will soon explode, but it will also cause more knockback and damage.
If the Bob-omb is not picked up after a while, it will begin to walk back and forward on the platform it spawned on, exploding if it hits any characters in its path. However in Super Smash Bros. for Wii U, it is possible to pick up the item just before it starts walking. If no one crosses its path, it will then stand still while flashing red, and then explode, causing damage and knockback to anyone nearby. In Smash 4, if a Bob-omb is close to any fighters, it will walk towards them when it starts moving, making it a bigger nuisance than in previous games.
The Bob-omb is also one of the various unusual items Peach can pluck via her Vegetable special move. The chances of her plucking the item is approximately 1/232, but in all games she has appeared in, it can potentially act as her most powerful attack.
In Sudden Death
If a Sudden Death lasts for too long, Bob-ombs will begin to fall from above the stage, instantly exploding upon striking players or the stage. They are intended to more quickly end a match, and unusually, they can be grabbed in midair. These Bob-ombs can be avoided by camping in certain parts of the stage.
The falling Bob-ombs do not appear in Super Sudden Death.
In Smash Tour
Introduced in Super Mario Bros. 2, Bob-ombs are bomb-like enemies that walk around, exploding after a short time. Jumping on a Bob-omb (except in Super Mario Bros. 2) stuns it: in this state it can be picked up and thrown, defeating enemies and destroying blocks with their explosion, which can also damage the player. If not thrown in time the Bob-omb explodes on its own, also damaging its holder.
In Super Mario 64, Bob-ombs react to Mario getting too close by igniting themselves and chasing after him. They can also be grabbed, and when thrown they explode immediately upon coming in contact with anything.