I nominate the family we had on our FL-NYC flight yesterday who had a seat for their child (not a lap) but refused to put them in it. They told the FAs they would move their child when it was convenient for them. FAs called us up during pushback to inform us of this.

The CA's response: Tell them it is convenient for me to move him now or we will have all of them removed from the aircraft.

Classic!

Needless to say the child was moved.