[Miscellaneous Android Development] martyfender:
Here is a list of apps I find useful.

1: Kernel Aduitor:

Turn off KSM and to tune vm and some other functions.

UPDATE: I now leave KSM on.

2: L Speed:

Primarily for it's built in GovTuner to improve performance and many other settings which may or may not be of benefit. Sign up for the beta in the playstore for the cutting edge. The lastest beta has an option to allow you to watch youtube in 4k, although this devices max is only 2k or 1440, but that is still better than the default. I generally don't use youtube that much, I prefer to read on xda, for example rather than view a fuzzy video on you tube. But if you search for 4k, you will be amazed at the quality. The first in the search, Costa Rica, is breath taking as are other 4k videos. There is a menu in youtube to choose the quality.

3: Greenify:

I also think Greenify is of some benefit if you don't get overly aggressive as to what apps you hibernate. Some apps don't have background processes, so don't need to be hibernated. Others, such as Kernel aduitor or lspeed, for example, won't function properly if Greenified.

4: Aida64:

for system information.

5: Apps2sd:

to move large apps, such as games to a second partition on your external Sd card to free up space. I don't recommend moving any system apps, though, it may cause unforseen Issues. Same applies to Greenify in hibernating system apps.

The program has a great system app uninstaller, convert user, to system apps, convert system apps to user apps.

As far as removing system apps, be careful. I only use it to uninstall google apps I don't use such as hangouts google play music, google play books nook app etc.

In other words, I don't try to remove apps that could potentially break the system.

6: Yahoo Weather:

Is a great weather app especially if you uncheck the default cities and add your own zip code. It shows weather photos from around my city. There may be better weather apps I haven't tried many, a couple I tried, I didn't care for.

7: Total Commander:

is a great root file explorer, enable root everywhere in it's settings.

8: Mixplorer:

is another great root file manager and photo explorer app.

In the past, I was a professional photographer, and I have many photos stored of my three sons, family and others, on Onedrive. You can add Onedrive, dropbox and others to view photos and files stored remotely. Use the latest beta version and add ons such as pdf reader, archive viewer and others.

9: Matlog:

is a great catlog viewer, based on the code of another great one, Catlog, with an updated user interface. I alpha and beta test L Speed and use it to submit bug reports to the author, using it's filter option to filter for that app.

10: YDS BusyBox Recovery Flashable Zips:

is a twrp, flashable zip installer without the bloat and advertising and is updated to the latest, stable binaries, frequently.

https://xdaforums.com/android/software-hacking/tool-busybox-flashable-archs-t3348543

11: Simple Reboot:

by the famed Francisco Franco, Is a great app to easily power off, reboot, soft reboot, reboot to recovery, reboot to bootloader and reboot into safe mode.

12: AdAway:

"AdAway is a utility for root users used to help manage hostfile entries. AdAway doesn't directly block ads; it limits unwanted ads by blocking servers that distribute those ads to websites." It will block ads in some apps, but it is primarily useful to block ads in web browsers, so don't expect it to block ads in apps.

Get the latest dev version here:

https://www.androidfilehost.com/?fid=817550096634744719

I recommend unchecking the default hosts and adding a mirror of Steven Black hosts:

http://sbc.io/hosts/hosts. This is info that came from the AdAway xda thread.

In preferences, enable redirections and add in redirection IP:

0.0.0.0 instead of the default 127.0.0.0 local host. This is supposed to be faster, but there is some debate regarding this.

Too many, or too large of a host file will slow down your device and web access so that is one reason the Steven Black host file is recommended.

There is one, huge host file source that is notorious for including every bad or undesired site it can add to its blocking list, and to slow the device down considerably.

(MoaAB) Mother of All AD-BLOCKING Is not recommended!

13: SwiftKey Keyboard:

This a great Android alternative keyboard with many great features such as a number row and many great themes. I prefer nickel or cobalt for clarify.

When I installed it initially on this new device, my favorite theme for clarity, nickel, didn't show up anymore. I Uninstalled and reinstalled an older version from apkmirror and logged on to my account and it showed up again. Maybe it was eliminated and was in my account preferences, not sure. In my opinion, nickel is the best, by far, for my old eyes. After I updated in the playstore, the theme was still there.

14: System Monitor Lite:

This is a great app to view cpu, ram, disk i/o, network, top apps, cpu frequencies, storage stats, charge history, battery stats and temperature usages.

15: SELinux Switch

https://xdaforums.com/android/apps-games/app-selinux-switch-t3656502

This is a root app that allows you to toggle Selinux status from enforcing to permissive if you happen to use one of the rare apps that requires permissive mode to function properly. Otherwise it is usually recommended to keep it in enforcing mode for security reasons.

It was created by respected forum developer [MENTION=4828250]Ibuprophen[/MENTION] .

Feel free to share any apps other users might find useful.