Walmart offers the Waterpik Cordless Water Flosser, model no. WP-360, for $28.49. Opt for in-store pickup to avoid the $5.97 shipping charge. That's tied with our mention from two weeks ago and the lowest price we could find by $2. This rechargeable flosser includes high-pressure and low-pressure tips, and is purportedly twice as effective as string floss.