Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
One of PopCap's most successful games, Plants vs. Zombies is an easy-to-learn tower defense title that's far more happy-go-lucky than it may sound. I mean, it's about sunshine, pea pods, and dancing undead. Who can't get behind that? With cheerful animations and simple but challenging levels, the only problem you'll have with this game is stopping.
Enter these during gameplay for the desired effect.
a shower of candy when a zombie dies
Alternate Lawn Mower appearance
Gives zombies futuristic shades
Makes the zombies dance
toggles the zombie's call for brains-sound
Zombies leave small daisies behind when killed
Zombies Now Have Mustaches
Fertilizer First Time
The first time Crazy Dave allows you to start growing your plants, you'll start off with two plants; upon feeding them enough water, Crazy Dave will say they need more fertilizer. Instead of buying the fertilizer, simply hit back. You won't get charged for the price of the fertilizer!