Interesting idea, although I really don’t have too many quirky automations actually running. I do still run an Arduino UNO + Thingshield (using very old code still) to act as a Temperature + Humidity, sensor Motion sensor, 4 door sensors, and 2 garage doors controllers. That was the project that started it all. I hope to replace the UNO/Thingshield with a NodeMCU ESP8266 in the near future as the performance is much quicker. I am hoping it is as reliable!
The washer/dryer monitoring system was something others in the community had come up with. I was planning on using an ESP8266 to monitor the power usage of each of these devices, and I had even bought a pair of clamp-on current transformers for the project. But then there was that awesome deal on the Aeon v1 power monitoring z-wave devices. It was too good a deal to pass up, and was nicely and neatly packaged already.
I have considered building a whole home power monitoring system, with each breaker in my panel being monitored independently. I just haven’t found the energy for that project 
The rest of my SmartThings devices are pretty normal - GE Z-Wave switches and dimmers, a few GE Link bulbs, ST Multi sensors and motion sensors here and there throughout the house, a water sensor monitoring the Air Conditioning drip pan, a siren, etc…
I really enjoy putting the puzzle pieces together with respect to the Arduino C++ world and the physical devices, sensors, and actuators. That’s why I am always intrigued by use cases other come up with. Here are some of the things that I’ve added to ST_Anything as user requests:
- RCSwitch (inexpensive 433MHz RF devices)
- Adafruit Thermocouple
- Dallas Semiconductor DS18B20
- A paddle wheel pulse counter to measure water flow using Arduino Hardware Interrupts
- A dimmable switch (using Arduino PWM output)
One of my other fun projects was tearing apart a Cree Connected light bulb to get its Zigbee module. I then connected this to an Arduino Nano and am able discern On/Off and 100 dim levels, each of which can be used to execute a routine on the Arduino as the user sees fit. Amazing how the NodeMCU ESP8266 modules are now so much cheaper than the light bulb + arduino hack!