Banzai Bill

Banzai Bills are a larger variety of Bullet Bills that first appeared in Super Mario World. These huge bullets are black-colored and have shark-like smiles. In the game, Banzai Bills are fired from somewhere off-screen and travel slowly towards Mario. Although they seem impossible to defeat, Banzai Bills are not very strong. In fact, they can be destroyed by simply jumping on top of them (just like regular Bullet Bills), although fireballs are ineffective against Banzai Bills.

Super Mario World (TV Series)
A Banzai Bill makes a minor appearance in the Super Mario World cartoon episode "Mama Luigi"; however, they were renamed Magnum Bills for the show. In the episode, Mario, after narrowly dodging an attack by a Koopa Wizard, accidentally leaps into the path of a Magnum Bill. Luckily, Mario manages to avoid being hit by this Magnum Bill, which simply flies off into the distance.

Super Smash Bros. Melee
Banzai Bills are a major threat in Super Smash Bros. Melee, where they appeared in the Princess Peach's Castle stage, randomly entering the battle, they would collide into the castle. Once burrowed into the wall, a Banzai Bill will detonate, causing massive damage to anyone caught in its explosion. The explosion will also press any buttons in range, activating platforms and ! Blocks. Also in Super Smash Bros. Melee, a Banzai Bill (as it looks like in Super Mario World) appears in the background of the Yoshi's Island stage.

Mario Strikers Chaged Football
Banzai Bills make a cameo in Mario Strikers Charged Football, in the Sand Tomb field. In this game, they only appear painted in one of the pillars in the background. Here, they are painted the same way they appear in Super Mario World.

New Super Mario Bros.
Banzai Bills reappear in New Super Mario Bros. These Banzai Bills look like their Super Mario World counterparts, except that their coloring has a slight purple hue, and they have red shadows under their eyes to make them look more intimidating. In this game Banzai Bills are fired from huge Banzai Bill Blasters (unlike Super Mario World, where they are fired from an unknown source). Additionally, these Banzai Bills travel very slowly, twirling in the air. Again, a simple jump is enough to defeat these massive enemies. They also appear in New Super Mario Bros. Wii, having a similar role. There is also a much larger variant, found in World 9-8, which is named the King Bill.

Super Princess Peach
Banzai Bills reappear in the game Super Princess Peach, which also introduced a red, more dangerous variant of Banzai Bills known as Mad Banzai Bills.

Super Mario Galaxy
In Super Mario Galaxy they appear in the game's last level, Bowser's Galaxy Reactor. They do not home in on Mario's position like Bullet Bills, but are difficult to avoid because of their speed and size.

Mario and Luigi: Bowser's Inside Story
A Banzai Bill also appears in Mario & Luigi: Bowser's Inside Story. In Dimble Woods, Bowser saw Private Goomp, Corporal Paraplonk and Sergeant Guy carrying a gigantic Bill Blaster where a Banzai Bill could be put in. They explain to Bowser that they are going to fire a Banzai Bill to Bowser's Castle, which was taken over by Fawful, as payback. The three, however, hadn't any Banzai Bill, so Bowser has to search one on his own. It seemed that a Wiggler on a farm had a Banzai Bill after Bowser pulled out his Giga-Carrot, what Bowser had to eat. After the carrot was eaten up, Bowser could choose to save or to get the Banzai Bill right now. If he asks for the Banzai Bill, the Wiggler gets mad because Bowser pulled out the carrot and ate it (which was quite ironic, since Bowser had to eat it for the Wiggler). After Battle, Bowser finally got the Banzai Bill and give it to Private Goomp, Corporal Paraplonk and Sergeant Guy. Then the Banzai Bill has been shotted to Bowser's taken-over Castle. However, Midbus and two other Goombas saw the Banzai Bill, and dodged it via flying.

Super Mario Galaxy 2
They also appear in a trailer of the upcoming game Super Mario Galaxy 2 and appear to behave exactly as in its prequel.

Trivia

 * In the Super Mario World cartoon, Banzai Bills were renamed Magnum Bills, which is a possible combination of the names Bullet Bill and Magnum Killer, which is the Japanese name of Banzai Bills.
 * Even though Super Smash Bros. Melee recognizes that there are only Banzai Bills in the game, the trophy is labeled as "Bullet Bill".
 * Enemies named Banzai Bills appeared in the game Hotel Mario. However, these bullets were not giant, and behaved just like Bullet Bills, instead of the Banzai Bills from other games.
 * In "Kirby Super Star Ultra", the boss Kabula (a giant airship with an evil smile and eyes painted on the hull) will sometimes fire a round of 3 to 4 giant missiles with evil smiles on them at once when her health is half-gone. These bullets look a lot like Banzai Bills and her face itself slightly resembles a Banzai Bill.