(18+ category) I'm 40 years old and I've constructed (with some help from my daughters!) this vibrobot (for those who do not know how they work, vibrobots shake due to the imbalance created purposefully in the shaft of their motors). I chose to call it Brushbrobot because it's a bristlebot, but big.
This is much easier to construct than a small bristlebot and has better performance (bigger pieces, no need for a special vibrating motor, more standard battery, longer autonomy, on-off switch added). It also allows for a rechargeable battery (highly recommended).
9V motor (lower voltage motors could work too)
9V battery (rechargeable recommended)
9v battery clip
Piece of wire (any color. I got mine cutting in half the red wire from the battery clip in half, which was long enough)
Unipolar on/off switch