Enlarge/ Check out the square fingerprint sensor (dead center) and the round hole in the case that exposes it (left). (credit: iFixit)
iFixit has dutifully torn down Google's newest flagship, the Nexus 6P, and the device certainly seems to have put up a fight. The aluminum unibody design is great for the build quality, but it means that taking anything out of the 6P is going to be tough. All the components come out in one big chunk, and after removing the case, iFixit said "the ultra-tight fit renders our plastic tools useless—we resort to a curved razor blade, safety glasses, and prayers."
The biggest surprise in the teardown was the new "Nexus Imprint" fingerprint sensor—it's square! Look at the phone from the outside and you would never know—Huawei made a round opening for the square component. Most of Huawei's fingerprint sensors—like on the Ascend Mate 7 and Mate S—have square fingerprint readers, so this was most likely a way to reuse the same components while keeping the design motif consistent with the Nexus 5X.
Interestingly, the device also has a Qualcomm SMB1351 Quick Charge IC despite the Nexus 6P and 5X not supporting Qualcomm Quick Charge. It's essentially just a power management chip, but search for the model number and you'll see that this exact hardware has been used to implement Qualcomm Quick Charging in other devices.