Cowboom offers the used Microsoft Xbox One Wireless Controller, model no. S2V-00001, for $39.99 plus $3.74 for shipping. That's $6 under mention of a new unit from three weeks ago and the best price we've seen for this controller. (It's also $9 under the best price we could find for a new unit elsewhere.) It features vibration feedback, an expansion port to connect other devices, and 30-foot wireless range.
Note: No warranty information is provided. Also, although these are rated as "9 - Like New," they may still show signs of use and might not include batteries or an owner's manual.