That probably largely depends on what you do. Apps I use all the time (ordered roughly by screen/activity time) are:
Overcast
Transit
MyFitnessPal
1Password
Reeder (for RSS)
Google Maps
Wikipanion (I hate the mobile web)
Fantastical
Camera+ (I only use the editing extension)
Authy (for collecting those pesky auth tokens)
Uber (when walking, bike or subway is not an option)
Other applications that make the phone much better:
Motion Stills (makes live photos presentable)
Lean (to save space)
Dropbox (better file sharing than iCloud)
Bring (best shopping list app)
Prompt (I still use irssi)
Why use Authy if you use 1Password? 1Password does everything Authy does (and more).
The ability to create one time tokens has been in 1Password since the beginning of 2015. https://blog.agilebits.com/2015/01/26/totp-for-1password-users/Huh, I did not know that 1Password could generate one time tokens, I'll look into that. Thanks