I have a lot of apps--most of which I don't use!
Key apps besides built-in Google stuff like Maps and Gmail:
--You need two eReaders. I chose Kindle, both to read Kindle and some other stuff. It's nice to have another for versatility and sometimes I have two things in progress. I pick Cool Reader.
--I like a customized music player. It is good for local files. PowerAmp.
--Security is essential. I use Lookout.
--I need to see my Docs and sync them. Docs to Go
--Evernote
--I use Firefox, not the stock
--My fave word game is Drop Words
--File management! the stock is simple, but I do like Astro. I used to prefer Andro Explorer, but on Jelly Bean it is less intuitive. Astro, however, doesn't let you perform searches AND multiple operations like "delete" from the results of the search. So I keep all 3.
--Some online storage apps if you use Google drive or competitors
---Tuned in Radio
--Mr. Number, nice help for blocking the increasingly obnoxious spammers who ignore the do not call registry list
--Skype, Google Voice
--RSS type of things like NY Times, Time, Cnn, Zinio
--I like Trip Advisor's city guides. If you travel a lot, it is a free guidebook in your pocket
--Amtrak's app is great
--Pocket is a great app for clipping from the web and reading off line
--Most printers with wi-fi have apps to allow printing from the phone
-History Eraser Pro--not because you watch porn, but because it erases caches of all apps at once, which used to be possible and no longer seems to be on Jelly Bean. It is good for space saving in a crunch.
"Watch apps"--if you have Comcast, they have a couple. Netflix. MX Player pro for videos, Crackle. IMDB for advice.