Plants vs Zombies is one of those games that seems like it was originally designed for ten year olds. But it turned out to be such an awesome game, that everyone has probably played it. And everyone that has played it, loves it.
The objective of this game is to place plants with horrible puns for names (like the pea-shooter which is the basic shooting unit, or the wall-nut which is a wall) to keep zombies from getting to your door.
The game gets really insane in some of the later levels, and you'll find yourself playing this for hours on end and not even realize it.
You can get this game for X Box live, PC, or the iphone, but really I'd suggest it for the PC simply because you can have better precision for the minigames, which are almost as addicting as the actual game.
Like all games, it has it's moments were it's not as good as it could be, but they are few and far between, mostly popping up when the screen is filled with too many zombies to count.
I'm putting this on my 'try before you die list', and if I were you, I'd go out and play this first chance you get!