Official Everybody Edits Forums

Command blocks:
Two options: Touch activated and interaction activated
Runs a command that you can choose
Maybe something to target specific players
Possibly a command to place/remove or edit blocks?

Health system
Spikes could have a option to change how much damage they did (maybe change the looks of them as they increase in damage)
Fire could slowly kill you like lava and lava would just kill faster than fire
In World options, maybe make a Default player health and/or a Health on? options

Crown Remove block (yea i know it's been suggested before but i thought of it too )

Doors? (Portal that you have to interact with to enter)

Dummy npc (Fake player that still triggers things)

I'll edit this if i have any more ideas!