HAT's
 
- Sense Hat; Acceleratometer, Magnetometer, Air Pressure and a few more
 - Automation Hat; plug and play with different type of outputs.
 - Pimoroni Unicorn; Just a led matrix hub, I don't like them a lot because you have tu put very close to the raspberry.
 - Adafruit Servo; as the name tell, control your step and servo motors.
 - pHat Beat; just a little Sound board.
 - HifiBerry DAC; co convert the digital signal to analog.
 - PoE Hat; if you would like to power on your raspberry over the internte, you need this. it's in my wish list.
 - Cluster Hat;to create server cluster
 - Uptime UPS; A funny solution to use as a external battery to protect and power your raspberry if there is any cut in the main power supply.