Have a look at the Orzly Tempered Glass Screen Protector for the brand new HTC One M8. Being only 0.3mm thick, the screen protector is super slim adding very little bulk to your device and making it compatible with almost any case. As shown in the video the screen protector is very durable against any knocks, damages and scratches.
Applying the screen protector is very easy however be careful to avoid any dust or fingerprints making contact with the adhesive side of the screen protector.
Where to buy: http://www.amazon.co.uk/Orzly%C2%AE-Tempered-Protective-Protector-SmartPhone/dp/B00J99QBZ6/ref=sr_1_3?ie=UTF8&qid=1401972164&sr=8-3&keywords=htc+one+m8+glass+screen+protector