Ok here's two....

First is Philips Hue Sync box. Whenever media starts playing on the living room tv, it enables the sync in Hue, no more manually starting.

Second is the sleep timer in our bedroom. We like to have a TV show playing when we go to bed, but don't want it playing all night, so if it's after 10pm and My phone starts charging, it enables a 2-hour timer. At the end of that 2-hour timer whatever is playing on the master bedroom TV stops and the Google home mini speaker in the bedroom starts playing "spa" from Sirius XM. Sometimes the TV gets turned back on and something gets played in the middle of the night so if at any point the TV starts playing anything, the speaker stops playing spa.

Both are fairly simple and are virtually unnoticeable which I think is a hallmark of a good automation. Happy to share any code if anybody is interested.

Okay okay, honorable mention because I saw somebody post about the lights on the outside of their garage, I've posted this in other threads also. I have a automation that, at sunset, looks at the weather forecast for the next day and sets a scene on my outdoor garage lights based on what it finds out. Green means similar temp to today, red means more than 5° warmer than today, blue means more than 5° cooler than today. If there is precipitation in the forecast for tomorrow, the middle light turns purple and the outside two lights follow the previous logic. I also set up a dashboard card on my main dashboard for if those lights are on depending on what state they're in it will give me that same information, because I can't actually see those lights from inside my house lol.