All HTC Android devices come with a locked bootloader (which is a nuisance and limitation many hate with a passion) which prevents one from flashing custom ROMs and other custom modifications that alter the system in any way. However, HTC does provide a way to unlock the bootloaders of their devices, which involves making an account on HTCdev.com and getting an unlock token which can then be used to unlock the bootloader.
Well, AT&T, Rogers and Telstra One X owners need not waste their time making an account and waiting to get an unlock token from HTCdev, as XDA Senior Member niceppl has released a script (adapted from a procedure by XDA member 18th.abn) that can unlock an HTC One X from either of the three carriers without any need whatsoever of using HTCdev, saving around 10 to 20 minutes of your time, as well as simplifying the procedure.
Head over to the official development page on XDA to download the script for Windows/Linux/Mac and get started with unlocking the bootloader on your device. There is currently no way to relock the bootloader, so make sure you are okay with that before going ahead with the unlock. Let us know how it works!