In the Games
Bruno is a member of the Elite Four. He raises Fighting-type Pokémon, living with them and training with them. He joined the Elite Four out of a desire to challenge the best Trainers. Although he trains Fighting Pokémon, he also uses Onix and its evolution and his strongest Pokémon is always his Machamp.
Bruno regularly visits the Sevii Islands. He and his Pokémon use the spa on Knot Island, and he visits Boon Island to buy RageCandyBars.
Brawly is a former training partner of Bruno's.
In Pokémon Gold, Silver, and Crystal, as well as HeartGold and SoulSilver, Bruno continues to be a member of the Elite Four, though moving up in rank one level.
In the Anime
In the Manga
Bruno was primarily a villain. He challenged Red to a Pokémon battle in a remote area and fought him evenly, defeating Poli and injuring his Pikachu and Gyarados. Afterwards, his comrades Agatha and Lorelei then offered a position on the Elite Four to Red for his battling prowess, but Red refused so Lorelei froze him using her expanding ice cuffs. Many of his Machop were seen to decoy Pewter City and keep Brock at bay before stealing his Badge.
Later, the Elite Four were at Cerise Island unleashing the final part of their plan: to destroy humanity. Bill and Lt. Surge encountered Bruno near an acidic river, with his two Onix acting as bridges. The battle took place with Bruno standing on one Onix, and his opponents standing on the other. When Yellow and Blaine came along it was also revealed that he put up a barrier to stop any intruders from entering so a fair battle could be fought. Bill and Lt. Surge eventually gained the upper hand by combining Exeggcute's Egg Bomb with Electrode's Explosion to make the Onix collapse and make them all fall except Lt. Surge had his Magneton create a Barrier to keep them elevated. It later was revealed that Bruno really used his Hitmonlee's legs to keep him hanging on, and Agatha's mind-controlling armbands then forced him to try and drag Surge down to the acid, only to be saved by a stranger with a Venusaur riding a bike. Red then came, revealed himself, and defeated Bruno using Vee with new found control of its evolutions.
It was later revealed that Bruno was an unwilling member, and only strived to be the best fighter there is. Agatha used the mind controlling abilities of her Ghost-type Pokémon to force Bruno to join. Due to this he was suffering memory loss and questions why he was in the Elite Four, so he couldn't even realize that he was being controlled.
Without any place to go, Bruno allied with three other ex-members of criminal organizations: Will, Karen, and Koga. Bruno apparently saved Koga when Cerise was about to collapse, and they both met Will and Karen in Ilex Forest at the end of the Gold, Silver & Crystal chapter. The new Elite Four, as they would later be known as, were not seen in action until much later, in the HeartGold & SoulSilver chapter.
Bruno attaches his Poké Balls to the ends of a nunchuck. The force of him using the weapon causes his Pokémon to be released at high speeds, giving him the advantage in battles. He also has a unique Hitmonlee with arms as flexible as its legs, something previously thought to be impossible. It has also been mentioned, similarly to the Generation III main games, that Bruno used to train with Brawly, now a Gym Leader in Hoenn.