I've recently gotten a coupon code from Diztronic that will get you 50% off all Samsung Galaxy S5 and HTC One (M8) cases. This only works for the next 24 hours so if you're planning on getting a Galaxy S5 then ordering a case now would be a good idea.
Coupon Code : D50GS5M8 [Only on Amazon]
Galaxy S5 Cases - http://amzn.to/S7eGxS
HTC One (M8) Cases - http://amzn.to/PP5QD9