Here's something that's always baffled me:
In overtime of an NFL game, if a team scores a TD the game is over. And, by rule, the winning team doesn't bother to kick the extra point (even though it's an untimed play) because it's moot -- since the game ends instantly upon scoring a touchdown, why bother?
Today, the Colts beat the Lions when they scored at TD on the final play of regulation, and, by rule, they had to kick the extra point.
Why? The game is just as over as it would've been if it had been scored in OT.
These nuances of the NFL rules keep me up at night.