Bobby Layne
One of the NFL's original gun slingers, Layne led the Lions to the franchise's first two championships in 1952 and 1953. He capped off his career by going 27-19-2 in five seasons with the Steelers, who had just two winning seasons prior to his arrival in 1958.
Warren Moon
Moon started his career in Canada before finally getting his shot in the NFL with the Oilers at age 28. Moon spearheaded a resurgence in Houston (who were just 13-35 in his first three seasons) that included seven consecutive playoff berths. Moon, whose patented deep ball helped him win back-to-back passing titles later in his career, was third all-time in career passing yards (behind only Dan Marino and John Elway) at the time of his retirement.