Flagship (noun)

1. The largest, most important, or most powerful ship in a navy, especially one that carries the flag of a commanding officer.
2. A company or organization's most important or prominent product or service.
3. The leading or most important unit or element of a larger group or system.

Origin:

From middle english flagge + -ship.

Examples:

1. The USS Constitution was the flagship of the American fleet during the War of 1812.
2. Apple's iPhone is often considered its flagship product.
3. The flagship store of the luxury brand was located on 5th avenue in New York City.
4. The flagship location of the restaurant chain was its original location in San Francisco.
5. The flagship university of the state university system was known for its strong programs in the sciences.