Rabbi Moshe Feinstein

Avi Shafran wrote in the Jerusalem Post on Oct 16, 2007 an article titled Star Power where he Quotes an answer written by Rabbi Moshe Feinstein in 1968 (Igrot Moshe, Orach Chaim 3:15)

to the question: is the Magen David symbol appropriate as an adornment for religious items? 

-the Magen David is an ancient Jewish emblem, and is therefore entirely properly displayed in synagogues and on religious objects.