I've got Emby tied into HA and it auto dims the lights on playback/pause if it's dark with a toggle in HA to override.

A "night mode" button that starts my white noise MPD playlist in the bedroom and sets the speaker zone/volume, turns off all the lights/decorations, turns on one bulb in the living room overhead lights to 1% (just enough to navigate around furniture), and turns the bedroom lamps on to medium brightness with a 10 minute auto-off.

Overhead lights and lamps tied into a common dimmer and can select different modes (lamps only, overhead only, both, etc) and color temps. Overhead lights are set to be proportional to the lamps to keep the light levels even (unless overridden to "Chernobyl mode" which disables the overhead light limiter).

My "TV" is just a PC connected to a large dumb monitor upstairs and a projector downstairs. Wrote a MQTT agent in Python to control turning the screen on/off, volume, and other settings. This is to allow HA to turn the screen/projector on/off .

Have more, but those are the ones I'm using this moment.