cool, fast and Blinky e-powered mule-device for having fun with and / or driving stuff from parking to camping place at camps and back
Blinkenlights? (remote controlled glowing ball, light-stripes, light cube platform, etc.)
Quadrokopter
Open Source alternative for Logitech Harmony Hub base on RPi and lirc
VR game
DoorButler, GateButler - open doors, garages and gates with an RPi, connection to OpenHab or Home-Assistant
FriendLoc - location based fried notification
HackerPi
Software Defined Radio - Rad1o
controll stuff with a esp8266 in a secure way
smartmirror