i don't remember the name of it but the perk that increases their money gen speed by the number of attack speed buff plants, at a certain point it's just a solid stream of yellow coming out the top of the sunflowers, it's no longer numbers haha
other combos that were fun was magnet capstone for the reach plant with the hyper fire rate plants, and placing watering plants at the beginning and letting them do the hard work for me c: