Pleco is a good one to have. It's a dictionary with character recognition, I use it all the time.

Citymaps2go is a good map app if you are traveling.

Didi Dache is pretty good if you can communicate in Chinese. It's the Uber copy for china. 

you can get tons of apps/ functions inside of wechat

1. Spoonhunt (ID: spoonhunt): Like yelp in the US, but translated to Chinese menu items into English, works all over China

2. wechat secretary (ID: we-secretary): a person on the other side you can as for help, some services they charge for

3. Wechat payment (built in, just link your card) - you can pay for your water, electricity, internet etc bills and also transfer money to friends, like paypal on steroids

4. Wechat translate- you can press and hold messages inside wechat if they are chinese it will translate to english

-Wechat (since you already have it, hold onto it)

-Baidu Maps (since Google Maps won't work anymore)

-KT-Dict or any offline CN-EN dictionaries

-Dididache and Kuaididache, although you will need to speak Chinese for that (or at least be able to clearly explain where you are and where you're going) - it's not like Uber in the sense that licensed taxis use it, I don't think unlicensed ones do (or can).

-Solitaire. It's always good to have it with you. Always.

I can only answer as an iPhone user, not sure if these are available for Android. 

Metroman - has all Chinese metro maps & good search function. 

Apple maps! Works well in China as the mapping data is from Autonavi (Chinese company)

Autonavi - fully functional and free GPS navigation app. I drives lot and this app is the dogs bollocks!

KT-Dict as mentioned above. Good dictionary (I prefer it to Pleco but it doesn't have OCR)

Waygo - OCR menu translator for the dishes I can't read. Very useful in restaurants without pictures on the menu 

Babelfish - text translator. Can use google translate or Bing. Obviously I use the Bing option as Google still blocked great for copying text from SMS's and translating them 

Here are some of the app I would recommend:

Traveling:
Living Abroad’s BT App
Packing Pro Packing Pro
Smart Traveler App
ExpatExpress
Didi Taxi
Kuaidi Taxi

Guides:
Explore Shanghai/Beijing/Guangzhou/Hong Kong
Open Door Guide to Shanghai
Shanghai Guide
City Fu
The Forbidden Palace
That’s

Money converter:
XE Currency

Internet/Radio/Phone credit recharge:
Douban.fm
Wi-Fi Finder
WeChat

Food:
China Menu

Dictionnaries:
Waygo Visual Translator
DianHua dictionary
Qingwen Mandarin Dictionary
Lonely Planet Mandarin Phrasebook
Pleco
Lingolook app

Maps:
Explore Metro Maps
Explore Metro Guide
Autonavi Navigation (高德导航)

Check out the pollution level:
Air Quality China
China Air Pollution Index

Shopping:
Taobao

News:
ExpatExpress
China Daily
BBC News