Melon-pult

The Melon-pult is a plant that lobs watermelons at incoming hordes of zombies. The melons smash on impact, causing damage to zombies within one square in any direction. Since its melons do 4 times the damage of a pea, and it shoots 1/2 times of a Peashooter, the Melon-pult has the same damage rate of a Repeater, but has a wider target and be used on Roof levels. Melon-pults also cost less than four Peashooters. The Melon-pult can fire over the shields of Ladder Zombie, Screen Door Zombie, and Trash Can Zombie.
Both the Melon-pult's shape and projectile are based on Citrullus lanatus, the common watermelon. This is the last plant you gain in Adventure Mode before the final stage.

Melon-pults can hit Newspaper Zombies, Screen Door Zombies, and Ladder Zombies over their shields, and Snorkel Zombies while they're underwater (like all lobbed shot plants). When you are planning to use catapults, you might want to start with a cheap lobbed shot plant, and replace it with the Melon-pult later. It is quite useful on the roof, as well, since it (like the other lobbed shot plants) can shoot over the angle of the roof, in addition to being the strongest catapult plant not obtained from Crazy Dave. You should also considerupgrading it to a Winter Melon later, if possible, as all the zombies in range will also be slowed down. Also, supporting Melon-pults with Kernel-pults is very effective, as you can temporarily paralyze zombies with its butter attack while melons smack them in the face plus additional area-of-effect damage.
Comparing two Melon-pults to a Gatling Pea and a Torchwood: A Melon-pult does only four peas of damage per second. Considering its splash damage, which is two peas per second in ideal conditions, its average damage per second per row would be, given a zombie density of one per square, 7. With a lower zombie density, this is much lower. A Gatling Pea and a Torchwood would do eight peas of damage per second, given a zombie density of 1 per square (and an extra four peas for each zombie on that square) while taking up the same space on the field. Also, the Gatling Pea and Torchwood combination (with the Repeater) takes up three slots in the seed tray. Given one zombie, three melons to die the two Melon-pults will do a meager four peas per second, and the Gatling Pea and Torchwood still does 8 peas per second. Once upgraded to winter melon, it is almost unbeatable.