BrainyDeal via Amazon offers the AGPtek 2.4GHz Wireless Optical Gaming Mouse
for $22.99. Coupon code "FB424U77" cuts it to $17.99
. Plus, Prime members bag free shipping
. (Non-members can spend $35 or more to bag free shipping; otherwise, shipping adds $8.25.) That's the lowest total price we could find by $4. It features an adjustable 2,500 DPI.