The Colonial Viper, the main fighter craft of battlestars in the 1978 Battlestar Galactica. Illustrator Ralph McQuarrie designed them for the show. His design drew heavily on the X-wing fighter he designed for Star Wars in 1976, with an almost identical nose, canopy, and paint scheme (color and design). Even the design for the engines was the same, although they were mounted differently. About the only thing McQuarrie did differently was to use three fins rather than wings.
The startling similarity between the two designs was one of the 34 copyright infringements cited by 20th Century Fox in 1978 when they sued Universal Studios for ripping off Star Wars. George Lucas, having seen the first three hours of BSG, was livid and pushed Fox to get involved in the suit. Universal counter-sued by claiming Star Wars ripped off Silent Running. A trial court granted summary judgement in favor of Universal, but this was reversed on appeal and a trial scheduled.
The parties settled out of court before the case went to trial. Although there are claims that Universal paid Fox (either a huge or small sum), there is no real evidence one way or the other.