1. It is completely legal to tackle someone by the hair. Also, if someone’s hair touches the ground he is considered down.
2. A team can kick multiple field goals on a single drive, as long as the other team does not acquire possession.
3. If the ball is hiked through the quarterback’s legs, it is a false start on the center, not a fumble. This is only in effect if a quarterback does not touch the ball.
4. Immediately following the fair catch, a team may choose to take a fair kick. This is when they may attempt a field goal, for 3 points, without pressure from opposing teams.
5. If a team does not send the appropriate number of players to the toss, a team may automatically lose the coin toss and be penalized for delay of game.
6. A team may be awarded a second chance on an onside kick. This happens if an onside kick fails to go the full 10 yards and goes out of bounds without being touched. In this case the team is awarded a 5-yard penalty and a re-kick.
7. A team may be penalized for playing leapfrog. During the kick-off, if opposing teammates jump over each other in order to catch or block the ball, they are given a 15-yard penalty.
8. A team may accidentally disqualify its top two quarterbacks from playing if the third-string quarterback enters the game anytime before the end of the third quarter.
9. A team can win an overtime game by nine points. This is a relatively new rule, that in an overtime game each team is guaranteed possession of the ball if the other team only scores a field goal. This means a team can score a field goal (3 points) and then, when the opposing team obtains the ball, intercept a pass and score a touchdown. By intercepting the ball and scoring a touchdown, the team seals the victory and wins overtime with a grand total of 9 points.
10. A player can be credited with a passing touchdown and a receiving touchdown on the same play. This happens if the quarterback passes the ball laterally to a player who then passes it back to him.
Source:
http://wlogblog.wordpress. com/2011/02/03/15-strange-things-that-can-technically-happen-in-football/