Using one type of plant implies that normally only a shooting plant is used. The easiest way to get One-Trick Pony is in the first levels where a few Peashooters will get the job done. In tougher levels, it is recommended to use a couple Aspearaguses, as it has a little more power than a Peashooter and has huge range for only 25 sun more.
In harder levels, the players may consider using the Lawn Mower to kill a high quantity of zombies while holding zombies by a Wall-nut. They may also use the Gardening Glove to move a strong shooting plant around.