Not a rule as such but more of a clampdown on where someone commits a foul, play is allowed to go on and the referee forgets to book the player when play stops. Also I'd like to see a bigger clamp down on diving, we still see a case of where players dive and the referee waves them to get up but doesn't book them.
I have to agree though that the celebration of taking your shirt off shouldn't be a red card offence.