After looking at hundreds of comic book covers, it becomes quickly apparent that not every cover is 100% original. Whether done intentionally or even underhandedly, there's something about uncovering these "swipes" that adds a new element of fun to reading and collecting comics. Even the Man of Steel isn't beyond swiping from Steranko's Nick Fury, Agent of S.H.I.E.L.D.
Nick Fury Agent of S.H.I.E.L.D. #6 Nick Fury Agent of S.H.I.E.L.D. #6
November 1968
Jim Steranko
Ka-Zar the Savage #34 Ka-Zar the Savage #34
October 1984
Paul Neary
Superman vol. II #28 Superman vol. II #28
February 1989
Kerry Gammill
On Ebay: Nick Fury | Superman On AtomicAvenue: Nick Fury | Superman