as a previous Facility rated controller at the busiest (military) airport on the west coast I can't imagine what would be more important than keeping an eye on traffic that is cleared for takeoff, just my 2 cents.
Nothing....but as a rated controller at an airport where we work SPO (single person operations) with ADI and APS duties for some HRS late/early each day, I can tell you this:
No matter how much the book says "never stop watching the traffic", when the ATIS is so old it's eligible for pension, the last snowtam sendt was 2 hrs ago, the field maintenance chief has called 3 times to coordinate XX (and the list goes on.....) , yeah, you drop the ball.
Is it right?
No!