Lieutenant Worf

Worf is the first Klingon ever to graduate from Starfleet Academy. He's in charge of security and is an expert on all types of weapons and armaments. His motto is, "To die defending one's ship is the hope of every Klingon."

Worf was orphaned in childhood during a Romulan attack on a Klingon outpost. He was rescued and adopted by a human Starfleet officer and his family.  The rest is history.