I've been using my M5Stick with lots of the example code it comes supplied with via the Arduino dev kit, and been experimenting with several hardware modules that I bought after getting it.
There's plenty of projects to do, such as remote controller using ESP-NOW direct messaging for my little BugC (Zippy little 4 motor robot), interfacing the Joystick unit to it, creating pritty animations with the LED display board Hat (full RGB color!), and also creating a super small robot arm with the C-Back Hat (4 servo driver).
They all work directly with the M5Stick and I've used it much more than my other M5Stack units, like the Core 2 and E-Paper. It's just so fun!
It's cheaper than the Core Grey and similar units, while still having a screen, buzzer, IR emitter, and inertial unit.
Unlike the slightly cheaper units like the Atom and Atom Matrix and Lite, it's got an in-built battery.
I think it perfectly hits that sweat-spot of features and price - and is a good starting device to begin your M5Stack collection with. =D