This post is targeted mainly at devices with 7inch screen size and above (tablets).
Many people who own tablets under-utilize them. though it may not be able to substitute a computer or a laptop, it can really enhance one's productivity, especially for people who love working "on the go".
I'm a technology enthusiast and majority of the apps i am about to list are more inclined to that aspect, but ihave no doubts that one can find apps to enhance productivity on any aspect, be it economics, law, business, etc
alright lets get to it

1. AIDE and AIDE Web : an android IDE that allows one to program java, c++, and also do android development. though a mobile application, it can actually be used to develop fully functional android applications and run them directly on your device. with syntax highlighting amongst other features that make programming a little more fun. i would suggest it to anyone who also wants to learn to code.
The web version of it also allows for web development ; html, css, php. one can create full functioning websites from scratch, with its own web page viewer which allows you to view your page as it would display on a web browser, it is a handy tool. once again i recommend for those who want to learn to code.
Worthy of mention here to is "Palapa web server" which works as a WAMP for android, the developers claim you can even host your website on ur android device and allow people access it over the web, only that our network providers might not allow such connections. other apps worthy of mention are DroidEdit, C4Droid, Qpython.

2. Adobe Reader and I-annotate pdf reader : personally i use adobe reader for all my pdfs, but i annotate offers multi tabbed viewing, meaning you can read more than one pdf file simultaneously like you would view many web pages in multiple tabs on your browser. worthy of mention here to is cool reader for reading other document types such as epub and mobi.

3. Analyze this and personal chess trainer : both wonderful chess apps that can enhance your playing strentgh. Analyze this comes with chess engines for analysing games and positions. perfect chess trainer comes with many features to enhance your understanding of positions and strategies for every phase of the game (opening, middle game and endgame).

4. CamScanner : scanning documents on the go

5. Droid Tesla and EveryCircuit: two awesome android apps for electrical/electronic engineers. its basically a proteus for android, where you can design and run circuits. great apps.

6.ConvertPad and SmartTools : convert pad allows you to convert from one unit to another while smart tools is a collection of tools that make use of your device's hardware to measure quantities such as distance, angle, sound, as well as having a plumbline and metal detector.

7. GPS Essentials: a very good gps application that lets you do tons of stuff.

8. Longman Dictionary and Medical Terms : Medical terms is a dictionary of medical related stuff.

9. Office Suite : Powerful collection of Word, Excel And Powerpoint.With almost full functionality of its PC counterpart. i actually created my present CV using this App.

10. PhotoEditor, PicsArt and Pixlr : powerful photo editing apps. i personally use all because of their individual features that i would want to incorporate into the image. so i just share them to each other incorporating my various tools until the final render .

11. Xplore and Solid file explorer: My two best file managers.

12. Duolingo : Powerful application for learning Languages. Also worthy of note is Google Translate.

13. Tasker : Super Powerful android application that can help make your Smartphone even Smarter by teaching it to think and react for itself. google it for more info. cant start typing long stories here.

14. Edjing and Fruity loops Mobile: Edjing is a dj application and Fruity loops creates music .

attached is a blurred copy of my CV (i still dey learn tho) to show well office suite functions.

feel free to add more

thumbs up

U try...every way na way

You tried, but Android has more better productive apps

Glad to see another AIDE user
But ES File Explorer is GOAT.

Kizyte:
You tried, but Android has more better productive apps

Thats why i said anyone cud add to the list. Of course i cant knw every android app on playstore

Add Eraser to your number 10 on the list.

ES file Explorer is really G. O. A. T

Knowing that it comes with everything in one package from media player, zip archiver , note editor etc..

All in one small app