(written from a Production point of view)
Donald "Don" Bannerman Pennington (born 27 June 1943; age 77) was a prop and studio model creator who has contributed as such to three Star Trek live-action productions, though he has only received official credit for one of them.
Don Pennington started out his motion picture model making career, when he received a call from a friend, which happened to be Gregory Jein, in 1979, asking him if he was interested to work on a movie for a day. Pennington jumped at the opportunity, having stated, "So I went over and worked 18 straight hours on Star Trek: The Motion Picture". Only a hobby model maker up until then, Pennington's visual effects coordinator, impressed by his abilities, hired him full time, and his one-day job turned into a two-month engagement. (The Spokesman-Review and Spokane Chronicle, Wednesday, 24 October 1990, p. C5)
Fifteen years later, Pennington received his only official Star Trek credit for his work on the Star Trek: Voyager pilot episode, "Caretaker". At the time, Star Trek's regular production staff was spread thin, due to the fact that several other productions, aside from the Voyager production, were concurrently in various stages of development, which were the final episode of Star Trek: The Next Generation, the season 2 ending of Deep Space Nine, the production of Star Trek Generations, and the documentary Journey's End: The Saga of Star Trek: The Next Generation. Several outside vendors had to be brought in to alleviate the pressure on the regular production staff, Don Pennington being one of them. Pennington's main responsibility was the construction of the breakaway model of the Caretaker's array (the main model being built by Brazil-Fabrication & Design), blown up for the episode's finale. Some of the debris of that model was signed by Pennington when they showed up in a 2008 auction. 
In 1996, Visual Effects Supervisor David Stipes needed a physical model for close-up shots of the newly conceived Jem'Hadar battle cruiser, which made its debut in Star Trek: Deep Space Nine's fifth season episode "In Purgatory's Shadow". By then however, hitherto regular studio model vendor, Brazil-Fabrication & Design, had wound down its association with the Star Trek franchise, partly due to the fact that the franchise was in the midst of a full transition to computer generated imagery, causing their services to be rarely required anymore, and partly due to the fact that Brazil was unavailable to the franchise at the time as it was knee-deep involved with the block buster movie Titanic (1997). Production Designer Richard James, who had worked with Don Pennington on the Afghan war movie The Beast of War (1988, and for which Pennington had built the Russian tank, albeit uncredited), brought the latter to Stipes' attention. Though concurrently likewise heavily involved with Titanic, Pennington was nevertheless able to free up capacity to serve the Star Trek franchise. Considered by his peers an expert in constructing models out of glass reinforced plastic, commonly known as fiberglass, it has always remained Pennington's method of choice, even though colleagues had already started to use newer and lighter composite resin materials. The Jem'Hadar battle cruiser model he eventually constructed was therefore quite heavy compared to contemporary products, or as Stipes himself had, only half-jokingly, put it, "The model was very large and with traditional materials it became very heavy. It took three to four people to safely lift and turn the model over for various shots. It was affectionately dubbed the "Lead Hadar". (The nick-name was earned; I know first hand as I got to help turn it over once.)".  Though a signature contribution, Pennington has not received official credit for it.
Career outside Star Trek
Don Pennington was a relative latecomer in the motion picture industry, already in his mid thirties when he got his position on The Motion Picture, but has remained ever since. Preferring to operate as an independent contractor, he started his own company , Don Pennington, Inc., under which flag he has plied his trade. Projects he, sometimes uncredited, has worked on were WarGames (1983), Ghost Busters and Splash (both 1984, constructing Darryl Hannah's fishtail for the latter), Cocoon (1985, in which he also dabbled as a stunt man), Where the River Runs Black (1986), and Harry and the Hendersons (1987).
In the 1990s Pennington has worked on the television series Lois & Clark: The New Adventures of Superman (1993), as well as on the movie features Flight of the Intruder (1991, Vietnam landscape maquettes, filmed by Image G, and working alongside Joe Lombardi), In Search of Dr. Seuss and True Lies (both 1994, and the latter of which he provided the Harrier jet model for), the documentary Michael & Janet Jackson: Scream - History in the Making (1995), Sgt. Bilko (1996), the video game The Journeyman Project 3: Legacy of Time (1998), The Thirteenth Year (1999), and Hollow Man (2000).
The production that brought Don Pennington renown however, was James Cameron's blockbuster movie Titanic from 1997, serving alongside several other former Star Trek VFX staffers . For that production he and his company constructed the large, highly detailed 1:4 and 1:6 scaled sinking models of the Titanic. It has earned his company an individual 1997 Visual Effects Society Award,  aside from helping win that movie its slew of Academy Awards. An in depth interview with Pennington on his Titanic builds has been featured in the British Effects Special magazine, issue 1.1. His last recorded motion picture credit was the 2005 movie End of the Spear.
Apart from providing models and props for the motion picture industry, Don Pennington, Inc. also constructed models for display purposes, including replicas of famous science fiction productions, such as the Discovery from the classic 2001.  It was one of these, a copy of the Jem'Hadar battle cruiser, that has stirred up some controversy in 2010, when it, through a private collector, was offered up for auction as Lot 1487 in the Profiles in History Hollywood Auction 40 of 12 June of that year, estimated at US$6,000-$8,000, and misrepresented as a screen-used studio model. Profiles was forced to pull the model from the auction at the last minute, when aficionado Alec Peters proved that the claim was a falsehood. 
Don Pennington currently enjoys retirement, and his company is no longer in operation.