Android Studio Emulator
Google's own development IDE for Android is an idea too. The Android Studio is to help developers create apps and games for Android, but it has a pretty capable emulator built-in as well.
This works great for developers, but if you're looking to mess around, play games, or use it as a consumer this isn't the best option. Just know that it is difficult to set up, but once you do, things will be much easier. Again, only use this if you're already into the Studio.