Beyond the obvious stock Google programs, a few apps you can't live without right now (and a quick word about why): Pushbullet and Pocket are really great. I spend a lot of time watching my son, and if he's playing peacefully by himself, I can browse the news. But some things I just want to push to my computer to check out later. Likewise, sometimes I find a nice long article that I'm not going to read in one go and save it to Pocket to read, either from my phone or my computer (or both).
As a developer, App Stats and Appmonger are great to keep an eye on how my apps are doing, especially after I release an update, but also during other events like competitors' updates or system updates.
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