Montgomery "Scotty" Scott ( James Doohan ). More commonly referred to as "Scotty".  Scotty's career began in 2243 and he served on a total of 11 ships, including a stint as an engineering advisor on the asteroid freight run from planet Deneva, making the cargo run a couple of times. 

Scotty's first served as Chief Engineer aboard the Starship Enterprise where he gained fame as a "Miracle Worker".   His knowledge and expertise saved the ship on more than one occasion.  Scotty also faced death numerous times while serving on the famous five year mission.  

Scotty died, killed by the space probe Nomad which also resuscitated him when commanded to by Kirk.    Scheduled to retire three months after the Khitomer peace conference in 2293 he has bought a boat in anticipation of having more free time.  Later that year Scotty was one of the honored guests at the launch of the Enterprise B.  Again he played an important role in saving that ship during the incident where Capt. Kirk was thought killed. 

Scotty finally did retire in 2294 at the age of 72, having served Starfleet for 51 years.   He was in the process of relocating to the Norpin Colony when his ship crashed into a Dyson Sphere, Scotty survived by rigging the transporter buffer for himself and another crewman.  Unfortunately the other crewman's pattern degenerated too far to be reformed.     He was subsequently found by the Enterprise E which loaned him a shuttlecraft for his own use ( "The Next Generation" ).   

Scott never married but had a number of romances including fellow crew member Mira Romaine.