if we had to pick one app that had come leaps and bounds in 2013, then Google Now definitely deserves to be mentioned in the list. Especially with Android 4.4, Kitkat, Google Now is integrated with the Home Launcher and as a result a more useful entity than hving to launch it manually using keys on your Android Device. Google Now has several commands built into it and the general perception is that people still do not know the true capabilities of Google Now and as a result still do not use it to do things it can. For example, I did not know that if you push in your confirmation E-mail of a package you might have ordered online to your Primary Mailbox then Google Now can track the package.
However, to help you out, here is an interesting infographic produced by the folks at CNET to help you understand the various commands that can be used with the Google Now so you can get the maximum out of the service: