Grounded from ALL activities for a week( this includes family outings)
Grounded from all material possessions(toys,games, TV, phone, computer, etc)
They are only allowed to change their punishment once a month.
Otherwise they would switch it to suit their desires. Ex: oh I have nothing planned for this week so I'll just give up activity privileges. It doesn't work like that lol
So guess which one they prefer and guess which is most effective(IMO)