Married couple filling separate tax return: In which cirstances this can be beneficial?

There are a lot of times this may be beneficial first that comes to mind is a couple who are separated with two households and two children they can both claim head of household. the second is when the two have vastly different incomes so the standard deduction for the smaller income makes it more profitable. or if one spouse has tax problems that would hold up the other spouses return (in the newly married category)...........R