This is more an aide memoire than anything else (in case of a phone rebuild), but it is the list of essential software I have on my phone at the end of 2015
Audio/Media
Google Play Music (so much better than Spotify for play lists and radio)
Dog Catcher (for podcasts)
Music Folder Player Full (the only decent player for displaying audio as it is laid out in the filesystem)
Productivity
Clockwork Tomato (The Best timer for the Pomodoro Technique)
Communication
Slack (a truly amazing team chat)
Twitter (The stock version is actually the best)
Facebook (Unfortunately)
System
Games
(I tend to not play games on my phone as I have a Nvidia Shield Tablet)
Sorcery 1 (or any choose your own adventure game)
Misc
Moovit (best for London bus times)
Plus mobile banking and mobile ISP provider’s app.