Plants vs. Zombies

One of the best tower defense games, Plants vs. Zombies, is free for iOS users; it doesn't matter if you have an iPhone, iPad, or both, you can download PopCap's addicting and ridiculously charming game for zero bucks. This is one of those times when, if you've thought, "Hey, I should try that game," you should download it immediately. And if you've long since deleted the game from your device, here's a reminder to redownload and play it all over again. Unfortunately, the Android version hasn't been discounted, and it's unclear if and when it will be. Also unclear is how long this offer will last, so just get it already.