What’s a gameplay feature you’ve NEVER used? New ideas to spice up your game!

I don't believe there is any feature that I have played through to completion and probably quite a few that I have yet to try.
I have only sampled new content because I did not want to progress my sims without University.

That's all changed now. :)
I have a group of about 20 sims that were never-aging young adults when TS4 had its first expansion pack.
Now all of them are toddlers, children, and teens with parents given to them through CAS.

I will probably try to give them each an aspect of TS4 to explore as they grow up. Their parents too.
I have not touched Cats and Dogs since about a week after it launched. I guess someone will become a Veterinarian.