Mista is one of the heroes of part 5, a part of Bruno's gang. When he was younger, he had a run-in with a group of gangsters, and was shot at. All of the gangster's shots missed, and that is where he saw an opportunity to pick up a gun, take aim, and shoot them all in the head. He was sentenced to prison for the rest of teenage years, and was eventually bailed out by Bucciarati, and passed Polpo's test. Guido tends to use a revolver as his firearm, and believes the number 4 is unlucky due to events from his childhood and the character for 4 in Japanese sounds similar to the word "die".
Sex Pistols is a stand composed of Six bullet like "people" living inside a gun, numbered from 1 to 7 (with no number 4). Guido can control the bullets to hit any direction and can do tasks when instructed to. Each "person" has different personalities, love to eat, if not fed, they will not work. It is very similar to Hol Horse's The Emperor.