Tower defense games have been done to death, but PopCap has breathed life into a often dull genre with Plants vs. Zombies.
Utilizing your gardening skills, with the occasional help of Crazy Dave, you have to harvest sunlight to grow an army of plants to destroy the hordes of approaching zombies. Each Plants vs. Zombies round starts with a clear lawn, and you have to build up your defenses, usually starting with sun producing sunflowers, then peashooters, and so on.
As you progress through Plants vs. Zombies you are given a larger armory including mines, bombs and more. While your capabilities improve, so do the zombies - you'll meet a range of zombies which require different tactics to be destroyed. The 60-minute demo gives you a great introduction to this really well balanced game. The attacking zombies are paced just right, so you're always under pressure to keep planting, while you have to do pretty badly to get overrun and lose.
The graphics are cheerful and detailed, while the sound features some amusing effects that never get irritating. The main game is broken up with mini-games, like bowling, which help to keep it feeling fresh. The mixture of real time strategy and cartoon zombies is pretty irresistible, and it's hard to imagine someone not enjoying Plants vs. Zombies.
Plants vs. Zombies is cheerful, fun, and a remarkably addictive game. Try it out!