Hi exprox. I'm sure you realize what you are asking is highly subjective. So with that in mind, here's my list.
Vital:
- Swype = Must have keyboard replacement
- Graffiti Pro = Keyboard enabling “Graffiti” handwriting on the screen. I am a former “Palm” organizer user and find this keyboard extremely useful for casual text input. I use Graffiti most of the time but switch to Swype when entering long notes.
- Pimlical Advanced Calendar for Android. = I rely on my device for my schedule, memos, todo and contacts. This Calendar app is my favorite. I does everything I need and more. I also bought and use the matching PC application Pimlical for Windows. The two are synchronized over a cable or Wi-Fi which bypasses the web. It takes some time to learn the two as they are full of features.
- MyBackup Pro = good backup program
- Documents to Go = good MS Office app. There are many out there equal, so try a few.
- CoPilot Live Premium USA = GPS app with turn by turn off line navigation.
- CamScanner = Snap a photo of a document just like a scanner.
- ES File Explorer = excellent free file explorer.
I obviously use my phone as a serious organizer and for business. I also have several other apps for fun and entertainment. For instance PowerAmp (music player), ProCapture (Camera app), ESPN Radio (I'm a sports nut), and several others. Scan the Playstore and filter the “Best of” and you may find apps you might like.
Also search these forums for past opinions of any apps you are interested in. This is a great place to get help.
Enjoy.