David Warren "Dave" Ellefson (born November 12, 1964) is an American bassist and Co-founding member of the American thrash metal band Megadeth from 1983-2002 and again from 2010-present. He has also been referred to as "Junior" to differentiate him from his band mate Dave Mustaine but does not go by this name professionally. Ellefson currently resides in Scottsdale, Arizona. In addition to playing bass guitar in Megadeth, Ellefson also has various side projects which include Temple of Brutality, F5, and Killing Machine.