big hitter
1. A person, group, or organization of exceptional talent, ability, influence, authority, or success. Ms. Smith's law firm is a big hitter in this city. I've become known as something of a big hitter in the company since securing that new client last week.
2. A product or brand that sells or has sold extremely well. Through its clever advertising campaign, this new vacuum cleaner has become a big hitter in the industry.