Although Gargantuar is a slow zombie, he has a high amount of health and can instantly destroy the player's plants by smashing them. Hypno-shroom, Garlic, Wall-nut, Tall-nut, and Pumpkin are useless against it. Once he is damaged enough, he will throw his Imp. The player must deal with his Imp as well as the Gargantuar. Even if the player's defense is good on the Gargantuar, if they lack defenses against the Imp, the said zombie will eat their plants and walk to their Roof Cleaners or chimney.
Since no Bungee Zombies will steal the player's plants, three of them will drop additional ambush zombies instead. A Squash or Cherry Bomb is recommended to prevent them from eating the player's plants.
Plant two columns of Sunflowers on the first and second columns. Plant a Cabbage-pult or Kernel-pult once you see the first regular Zombie.
Plant a column of Cabbage-pults and Kernel-pults on the third and fourth columns. Once you have enough sun, you can plant the Fume-shroom and Coffee Bean. This will damage multiple zombies on your lanes.
When the Gargantuar shows up
It is not advised to use Ice-shrooms and Doom-shrooms with Coffee Beans, because they have very slow recharge. Instead, use a Squash and then a Jalapeno for good defenses.
Only use instant-kills for emergency once the Gargantuar has thrown its Imp. This is a good way to prevent very slow recharging.
Replace the second lane of Sunflowers with Kernel-pults. This will cause more butter to come out and stun the zombies.
When the Bungee Zombies drop ambush zombies, avoid using the Cherry Bomb early. Once too many zombies are close to the empty Flower Pot, use the Cherry Bomb to deal more damage to the Gargantuar and destroy all the other zombies. Then, use the Jalapeno to destroy its Imp.
It is recommended to use the Jalapeno after the Gargantuar has thrown his Imp, as the Jalapeno will destroy both of them.
A good strategy is to Pumpkin important plants that could be eaten by Imps, such as Melon-pults and Winter Melons.