Nom Nom Nom

Difficulty: Hard-Extremely Hard

Nom Nom Nom is an achievement in Xbox Live Arcade, PlayStation Network, and PlayStation Vita versions of Plants vs. Zombies. In order to complete it, the player must complete a level only using Sunflower, Wall-nut, and Chomper.

Strategies
You should get this achievement on a day level where the number of zombies is low, since you cannot use extra plants (Lily Pads, Flower Pot), and also because most of the zombies are effectively the same, due to the fact that the Chomper is the only offensive plant you can use.

You should pick the Sunflower, Wall-nut, and Chomper (pick any other plant, but do not plant them). As the achievement states, you can only use three types of plants to win. If you plant another plant, you cannot achieve this. A good candidate to try to achieve this is Level 1-1. Plant Wall-nuts to the bery right to stall the earliest zombies, and then attack them with Chompers. If need be, dig up and replace Chompers in order to reduce the chewing time at the expense of sun.

Note: If the player places any other plants, even if it does not kill a zombie, he or she will not achieve this.

Trivia

 * In the description, it says Wallnut instead of Wall-nut.
 * The name Nom Nom Nom is probably based on the one of many ways of expressing eating with words. This may be an also reference where Wall-nut and Chomper were roommates in college, according to the Tree of Wisdom, or the internet meme "Om Nom Nom Nom", which originates from Sesame Street.
 * The lawn ornament in the Xbox live version is a Wall-nut, Chomper and Sunflower totem, carved out of wood.
 * Nom Nom Nom cannot be achieved on Level 5-5, even if the player does not plant any Pumpkins or Cherry Bombs. This is because there are Flower Pots.
 * This achievement cannot be achieved on any pool level.