Salvatore Valestra was a minor character in the animated film Batman: Mask Of The Phantasm. He was a powerful mob boss in Gotham City who suffered from lung cancer due to excessive smoking in his younger years, causing him to rely on oxygen tanks to help him breathe. His condition earned him the unceremonius nickname "The Wheezer". He was voiced by Abe Vigoda.
Ten years before the film's events, Valestra and his associates Buzz Bronski, Chuckie Sol and an unnamed trigger-man (who would later become The Joker) put pressure on banker Carl Beaumont to pay back a large debt to them. Unable to pay up, Beaumont and his daughter Andrea fled the country and travelled to Europe. Valestra bribed Carl's assistant Arthur Reeves into giving up his boss' whereabouts and sent his top hitman to kill him.
Ten years later, Valestra's criminal empire has greatly weakened thanks to the presence of Batman and the clean-up of the Gotham Police Department by Commissioner James Gordon. To make matters worse, Valestra's old lieutenants are being hunted and killed, supposedly by Batman (though the murders were actually committed by the Phantasm). In desperation, Valestra meets with the Joker and hires him to find the assassin and take them out.
The Phantasm later goes after Valestra and arrives at the crime boss' mansion. The vigilante spots Valestra in his armchair, his face hidden behind a newspaper. When the Phantasm pulls the paper away, Valestra's mouth is pulled into a grotesque rictus grin, courtesy of the Joker's signature poison. While it is not mentioned directly, it is implied that the Joker tainted Valestra's oxygen tank with Joker Venom.
The Joker had killed Valestra himself and left his body as a decoy along with a camera so that the Clown Prince of Crime could discover the true perpetrator of the mob murders.