We're all waiting for PopCap to get Plants vs. Zombies on Android, but developer lzn1007 goes a step further, and has released pvz -- a near-perfect clone. Pvz has three modes, Day Mode, Night Mode, and Challenge, which correspond pretty closely to the original. There's also two challenge modes, and they, too are essentially the same as the authorized version. Speaking of the authorized version, I fully expect this one to get taken down for trademark or copyright issues. I'll let the developers duke it out over those, I just wanna kill some zombies.
Fair warning -- the application asks for some permissions you're not going to care for, like location and phone state. There's an online social-gamer component that goes through a Chinese service called WiYun (use Google Translate, link is in Chinese, and seems legit), but you can leave it disabled and play offline. I tested it here with WiFi and mobile data disconnected and had no problems. I also ran it through Lookout, which didn't find anything glaringly wrong. When it's all said and done, I'm certain that enabling the online component means your submitting data to the developer, so use your own best judgment. There's a video, and download link (free, all versions of Android) after the break.