Years ago taxied out at DFW and ended up head to with a Saab waiting to go off 18L. Tower cleared Eagle to takeoff and they replied they couldn't go yet, they had to burn another 50 pounds of fuel to get under takeoff weight. Got to love ACCARS.
A LONG time ago at the flight school I taught at a Fed had the student work the W&B down to the pound to see if they could make a flight.
A limit is a limit, yeah it'll fly but if something happens you're as guilty a pound over as a ton.