Apex Launcher (by author Android Does)
- Android only
- Free basic version, $4 advanced (I use free)
- Replacement homescreen (a.k.a. "launcher" app). Thinking outside the app, Android lets you replace your homescreen (desktop) if you don't like the finer points of how your phone's included homescreen and app drawer work. I use Apex because it is fairly low memory use and allows me to change some visual settings which normally require "themes" in other launchers. I can change the dock background and spacing of dock icons, the default menu options, and how the app drawer organizes icons. Another good low-memory-usage launcher with a lot of features is Nemus. It also lets you modify shortcut icons with your own images and modify the text.
Power Toggles (author Painless Death)
- Android only I think
- A customizable widget with quick toggles and other shortcuts to various phone settings (e.g., airplane mode, ring/silent, GPS on/off). It can be placed on your desktop or on the notification drop-down screen. Also can link to apps. Custom icon and background colors, and lets you set your own images as widget background.
OI File Manager (author OPENINTENTS)
- Best file manager without a bunch of creepy permissions required. Can sort all folders by modify date (other sort options as well), so it is easy to see where some stupid app dumped a file. If you are browsing through folders, OI remembers where you were in the upper-level folder when you hit the back button, so you can peek in and out of folders without getting reset to the top each time.
QuickPic (by alensw.com)
- Reliable and stable picture viewer. Nice interface, various sharing and moving options. Can sort folders by date (and other options) so you can quickly find images saved to various other apps' folders. Also finds and thumbnails videos. Also a better way to find image files when another app prompts you to choose an image.
Lux Auto Brightness (by Vito Cassisi)
- Free basic, $3 paid for additional settings options
- Auto brightness control, my favorite feature being the ability to ONLY adjust brightness when the display first turns on, and it then remains at that brightness until next display off/on. I hate it when I am reading some long article, and the display keeps changing because of exactly how my phone is angled to light and other environmental changes. It can also use either the phone's brightness sensor or either back or front cameras as a light sensor. A lot of phones have wacky auto brightness, and some don't have it at all.
Aurora Universal Search (by 3CrownTech)
- A search widget/app (can add to desktop as either) which searches all of your phone's apps and files. Good replacement now that Apple has decided that they invented file searching and Android was forced to remove the official version.
Photo Editor (by dev.MacGyver)
- Free (add supported) or I think $3 (in-app payment, can't remember) to remove ads.
- Real photo editor. Resize, crop, add text, rotation, undo, various curves/levels/color/tone/contrast/noise adjustments, drawing. Better used on a tablet.
MX Player (by J2 Interactive)
- Free (ads when paused or using MX file browser) or $5.70
- Extremely versatile video player. It seems to play everything. Great interface, options like remembering last play location in video, set horizontal/vertical, double volume beyond normal system limit (great because a lot of videos have strangely low volume). I use the free version, and almost never see any ads. I use QuickPic to browse videos, and it lets me choose MX as the app to open videos and I go directly to play mode without seeing ads.