Google Now - best thing ever.. Definitely a unknown and underutilized app to most people.

CamScanner: I highly recommend this is you ever need to keep record of a receipt/document or even sending a signed document. It auto sizes the picture and sets the image quality perfectly. From there you can convert it to PDF and email it off or save it.

Chromecast: Picked up 4 chromecasts recently...best thing ever.

FolderSync: Auto backup pictures to various sources such as Google Drive, awesome

ES File Explorer: great for capturing APK's

Spotify
Skitch
Craigslist Mobile
Google Drive
Google Keep
Google Currents
Google Voice

Plus some others for work stuff..