Once again, football season is upon us, and once again, the occasion brings with it all the marketing mayhem, fan frenzy and trash-talking that sports are so often heir to. Pro football is unique among American sports due to its sheer, outsized spectacle. It's louder than baseball, brasher than basketball, and more routinely violent than the phenomenally physical sport of NHL hockey and the high-speed lunacy of NASCAR. In fact, of all the major sports in North America, football is arguably the one that brings out whatever vestiges of machismo might be lurking in even the most seemingly mild of fans.
Football, after all, is for manly men. But there are many types of toughness. Mental toughness (Jackie Robinson); quiet toughness (Gregory Peck, Gary Cooper); gritty toughness (a weary, determined American Marine); crazy, spasmodic toughness (Cagney's sociopath, Cody Jarrett, in White Heat); run-right-over-you toughness (Jim Brown); and on and on.
Here, LIFE.com offers a look back at some of the iconic faces and personalities that, in their own time and in their own chosen pursuit, were tough enough to answer that age-old question: Who's the man?