The woman who lives next to my DS and wife has a difficult 3 year old - he refused to get into his clothes for nursery so she took him in his p.j.'s ! I don't think he's done it again.
Ignoring it at home is fine but what about a public tantrum ? I has seen kids scream with rage all around our large supermarket to the distress of other shoppers. Perhaps leave the shopping and leave the shop, or shop on a day when the child is elsewhere could be the solution. Though this is not always possible. Often the rage seems to stem from the fact that the word 'no' has been used. I've seen children munching down on crisps and sweets just because mum can't be bothered to set ground rules.I used to give a mini-lecture to mine before any shopping - you are rewarded for good behaviour not bad.
My DD used to throw herself on the floor with rage, so we used to walk away, she then followed us and more rage - we moved again, eventually she got fed up