Does what it says in the title, 10% off Hotels.com if you have UNiDAYS membership (free for students) - it generates a unique code each time you click 'Get now' on the page.
While it's a whole 1% less of a discount than the Expedia deal I posted have found this deal works with hotels excluded from other deals, plus Hotels.com is sometimes cheaper than Expedia. You do not accrue nightly rewards if you use this coupon.
Just noticed that the terms on the Hotels.com website have a June 2017 expiry but it still works fine for me.
there is pretty much always a 10% off code for hotels.com (which does not accrue nightly rewards )