While browsing ebay.com (I believe in Chrome) today on my mobile device a $5.00 off coupon appeared at the bottom of the screen. I'm pretty sure I wasn't logged in on the browser. (I do use the app as well.)
If I remember correctly the coupon is good until 1/31 and must be used on a mobile device. May stack w/ todays %15 off, i dunno as I've already used that offer..