Here are three very essential Android phone apps to avoid some major frustrations:
For battery life: Autosync
When your phone is expending so much of its battery life just trying to keep up with pollling for Wi-Fi and GPS position and updates and notifications and syncing, battery life dwindles quickly.
This app at least turns off Google constantly syncing when you don't need it.
Note: To clear your phone of unseen battery drainage, it is good to reset to factory now and then.
For Hearing while phoning: AutoSpeaker
Auto speaker turns on your speaker when calling, a big benefit for those with less than the best hearing. The phone otherwise turns off the speaker as you hold it to your ear.
For making space for apps: MovApp2SD (and similar)
If your phone has room for an SD memory expansion card, these are apps which will give you more space to hold apps in general.