You have to be a little crazy to play football, but just like with rugby and extreme sports, football attracts crazy people. The difference between the two sports is football players get paid more and get more fame or, in this case, infamy.
I had a hard time ranking the first part of the list. The marginal players are hard to rank because crazy comes in multiple forms. Nobody would argue that Ronnie Lott isn't crazy because he had the tip of his finger CUT OFF to keep playing. On the other hand, Lott is smart and articulate off the field.
However, Ricky Williams never did anything on the field to make you think he was crazy, but he almost threw away millions of dollars because he didn't want to stop smoking weed.
So, how do you know when somebody is crazy? Here's a story that might shine some light on the situation:
When I was growing up my dad was transferred multiple times, and I switched schools often. I attended a small Catholic school and was a top five class clown until third grade. Then I transferred to a large public school and dropped out of the top 50 class clowns. How did I know I wasn't as crazy? I knew I wasn't as crazy because I thought spit wads were horsing around, as opposed to other kids who pulled other student's pants down for fun.
With some things, you just know.