I made a similar post not too long ago if you want to check there.
http://forums.androidcentral.com/google-nexus-7-tablet-forum/196029-must-have-apps.html
I recommend an app for your keyboard (Swiftkey or Swype or whatever), Tapatalk (if you like forums), and Rotate (to keep your home screen in landscape mode as well as many other screen orientation options).
Pulse (news), Elixir 2 (adds useful info and icons to notifications area + other options), Netflix, Pandora, Solitaire, Sudoku.... just to name a few that I use regularly.
Also, games I like are:
Gem Miner 2- fun and simple, but can be challenging. You play as a miner who digs around underground for valuable rare items and ores, but also have missions to accomplish like saving people or finding your way out. You can try the first Gem Miner for free as a demo.
Bakery/Restaurant Story - Free game but very addictive. It's sorta like Farmville or one of those games where you get to decorate and make/create things that take time in real life.
The Island: Castway - Similar to the Sims Castaway game, good storyline and fun. There is a trial demo.
Grow - I highly recommend this game, similar to Spore and Osmos HD, but very fun and good controls! You play as a little fish but as you eat smaller fish, you grow bigger and bigger and learn new powers and evolve. Try it!