Consistently as in through out it's life span? None. As the plant ages and the circulatory system gets smaller and more diffuse the fruit size declines.

Consistently as in almost guaranteed to get a few really big fruit from the variety each year? Well Delicious once held the record but I don't knwo if that is still true. Big Zac is another often mentioned, Giant Belgium another.

linked several discussions about the question from over on the Giant Vegetables forum below. They have many more suggestions in them.

Dave

Here is a link that might be useful: Giant tomatoes discussions