Hasoon2000 has released a GUI for Windows based machines that allows you to automatically root your HTC One M8 with just a few clicks. The All-in-one toolkit will install HTC drivers onto your Windows machine, do all of the HTCDev steps required to unlock your bootloader and flash a custom recovery.
I would debate whether this is an all-in-one toolkit, as I don’t see any options to install a superuser listed, nor any instructions post-recovery, although it does do a lot of the basic foundational actions needed in order to get to root. So it’s useful for anyone who doesn’t want to have to hunt for drivers or a recovery.
Those who are looking to fly completely under the HTC radar while rooting might be advised to stay away from this, as you will send your device ID to HTC in order to get the unlock token back, but it will do it correctly for you.
The toolkit includes TWRP 188.8.131.52 for the recovery, although you can choose to install your own if you want. I’m personally fond of PhilZ Touch, as it was working right out of the gate and some TWRP variants were being a bit of a pain, but your desired recovery is up to you.
The only word of caution I would advise here is that this is doing a lot of operations that you might want to understand for later root knowledge. If you don’t understand how to use fastboot to install a recovery, you might run into a situation where you’re stuck. Then again, I guess you could whip out the all in one toolkit and flash from there.
If you’re looking to fly below the radar and you’re not on Sprint, go and check out Firewater. If you’re just wanting something that will do most of the rooting for you, go ahead and check out this toolkit. It’s pretty neat.