Definitely QuickSave with multiple slots or at least Rewind or just time travel of sorts.
Fast travel should be a thing.
We almost have duplication with 3D printers and full duplication with software.
Auto-Tune? It's called service plan IRL.
Another great mechanics would be:
Respawning - "Dying is awesome! All of the cool kids are doing it!" -Borderlands 2
Magic - who need physical effort to do stuff, and even bother with guns?
Overlay GUI with absolute info on people, objects, and of course, yourself.
Built-in communicator + internet. No more worries about forgotten phone or no internet reception in time of need for quick lookup!
Absolute display of experience, skills and its levelling progression.