Just 3 plants okay and also do Upgrades
I like:
Day : Potato Mine, Chomper and Repeater
Night : Grave Buster, Ice-shroom and Doom-shroom
Pool : Threepeater, Jalapeno and Torchwood
Fog : Plantern, Cactus and Starfruit
Roof : Garlic, Umbrella Leaf and Coffee Bean
Upgrade Plants : Gloom-shroom, Cattail and Gold Magnet
Those are my 18 favorite plants. What about you ?