Gyroscope

The gyroscope uses a motor found on some DVD player (see picture), it is possible to use smaller motors and design a dedicated adapter.

It requires also 4 ball bearings 8x22x7 (I got them from an old fidget spinner)

The balanced version (2nd video) uses 3 AA batteries, and once at speed it keeps the orientation of the disc, while the unbalanced version (1st video) has only one battery so that it creates funny movements after spin it manually.