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.
The falling Bob-ombs do not appear in Super Sudden Death.
In Smash Tour
A bomb for a body, burning fuse on top, two little legs and a wind-up key spinning away on the back... We probably don't need to tell you what's going on here. Now, that doesn't happen too often! Then again, who knows? Maybe some people will look at a Bob-omb and think it's an eight ball having an identity crisis.
The ultimate glitch  is a glitch in Super Smash Bros. discovered by Isai. It involves picking up an invisible Bob-omb and waiting for a crate to fall on a player in the immediate area, upon which the Bob-omb would explode, causing the area where the crate fell to be engulfed in an infinite explosions created by multiple Bob-ombs. The invisible Bob-omb can be obtained by random. This can only occur if the Smash crate is a explosion crate in which it's containing more Bob-ombs.
In Super Mario Bros. 2, Bob-ombs were bomb-like enemies that walked around and would explode after a short time. The Bob-omb could also be picked up and thrown at enemies, though its resulting explosion could also harm the thrower. Bob-ombs reappeared in Super Mario Bros. 3, and if the player jumps on a Bob-omb it would become stationary. The player could also pick up the Bob-omb and throw it at enemies; however, the Bob-omb would explode after a few seconds after being jumped on. In Super Mario 64, if the player gets close enough to a Bob-omb, it ignites itself and chases after the player. They can also be picked up and thrown, but explode immediately after hitting the ground.
In the Smash Bros. games, a Bob-omb will stay at a spot for a short period of time. After the short period of time, it will walk around and self-destruct. The Bob-omb exploding on contact to whatever it hits is a reference to their behavior in Super Mario 64.