Due to the way you used slashes in the phrasing of your question, it's a little hard for me to figure out exactly what you meant. But John Jacob Astor IV was a prominent real estate investor who built the Astoria hotel (later the Waldorf-Astoria), and he was among those lost.

As maturin mentioned, John Jacob Astor was probably the most well-known figure who died. Benjamin Guggenheim, another prominent businessman, was also lost.

Another notable figure (though his notability was related to the Titanic itself) was Thomas Andrews, who played a major role in designing the ship. You may remember him as a secondary character in the 1997 film.

Archibald Butt was one. He served both Theodore Roosevelt and William Taft as a military aid. He was a close advisor to both men and his letters have served as a source for information on both of them. If you are interested, there are two volumes, "The Letters of Archie Butt" and another one entitled "Taft and Roosevelt: The Intimate Letters of Archie Butt".