From the Super Mario Wiki
Barrels are one of the two weapons that Donkey Kong used against Mario in Donkey Kong arcade game. Since then, barrels have appeared in many other Donkey Kong and Mario games, but they are more common to appear in Donkey Kong games. Barrels can be picked up and used to attack Kremlings, Koopas, and other enemies.
 Donkey Kong series
 Donkey Kong
In Donkey Kong, the first threat Mario ever faces is from a blue barrel that Donkey Kong throws in level 25m. When a blue barrel rolls into an Oil Drum, it will spawn a Fireball. Donkey Kong mostly throws brown barrels at Mario which Mario could jump over them (gaining 100 points) or smash them with his hammer like blue barrels.
 Donkey Kong Jungle Beat
In Donkey Kong Jungle Beat, barrels are used to transport Donkey Kong to kingdoms. Barrels act as worlds on the world map. There are four barrels, each linking to four different kingdoms. Each barrel has a letter in front with each letter spelling out the initials of Donkey Kong Jungle Beat. The D Barrel links to the Banana Kingdom, Orange Kingdom, Watermelon Kingdom, and Apple Kingdom. The K Barrel links to the Strawberry Kingdom, Pineapple Kingdom, Lemon Kingdom, and Grape Kingdom. The J Barrel links to the Cherry Kingdom, Peach Kingdom, Melon Kingdom, and Durian Kingdom. The B Barrel links to the Pear Kingdom, Lychee Kingdom, Chili Pepper Kingdom, and Star Fruit Kingdom. Completing all the kingdoms in each barrel allows Donkey Kong access to the next barrel.
 Donkey Kong Country Returns
Barrels reappear in Donkey Kong Country Returns, where they can be used to take out enemies again.
 Super Mario series
 Super Mario Bros. Special
In Super Mario Bros. Special, Barrels are new enemies and credited "Tarusar". Also, they can be defeated with a bump or a hammer.
 Super Mario Sunshine
Super Mario Sunshine included items known as Water Barrels, which can be broken open and used to refresh F.L.U.D.D.'s water supply, clear large patches of Graffiti, or to instantly cool things down. Also, it is an item.
 New Super Mario Bros. Wii
Barrels also appear in New Super Mario Bros. Wii. They can be carried and thrown by the player in order to defeat certain enemies. However, they can also harm other players if they get hit by one.
 Super Mario 3D Land
 New Super Mario Bros. U
 Super Smash Bros. series
Barrels also appear as items in Super Smash Bros. and Super Smash Bros. Melee, where they contain one to four items and can roll along inclines. They also sometimes explode when broken. They return in Super Smash Bros. Brawl, alongside the Crate. This time around, they change appearance depending on the stage. For example, it turns into a Present Barrel on the Yoshi's Island stage; though the effect of the Barrel remains unchanged.
 Paper Mario: Sticker Star
 Types of Barrels
 Super Smash Bros. Melee Trophy
 Super Smash Bros. Brawl Trophy
 Names in Other Languages