Dark mode, or at least a dark keyboard option
Dynamic content in iMessages e.g. Links show previews of content, videos show thumbnails, etc
Improvements to iPad multitasking - 2 instances of same app side by side e.g. Safari
Dynamic/subtle motion on icons like new Apple TV
Generally refreshed icons throughout entire system
New sounds (ring, text etc)
Fl.ux like feature which optimises display at sunset/nighttime so it's less stark, bad for eyes
Auto low power mode at 20%
Voicemail for FaceTime
Ability to type queries to Siri (alternative to using voice)
Weather and Calculator apps for iPad
Per-app rotation lock
More control over Do Not Disturb scheduling
Per-contact read receipts
Fix AirDrop (temperamental at best at the moment)
Letting UK users have 12 hour time with AM/PM (e.g. 4:58 PM)
Ability to snooze Messages and Mails to reply to them later
Sleep Cycle-esque Alarm app which uses accelerometer/sound to wake you in light sleep phase
New photo filters in Camera app (much needed)
Touch ID on Hidden Photos album and per-app in settings
That's a few off the top of my head. Bug fixes and under the hood optimisations obviously a given.