As one of its daily deals, Amazon offers Prime members the Logitech Trackman Marble Mouse, model no. 910-000806, for $15.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $8.54.) That's the lowest total price we could find by $7. Features include ambidextrous trackball design, USB, and fingertip-based control. Deal ends today.