Download PwnageTool 4.2 for Untethered iOS 4.2.1 Jailbreak
iPhone Dev Team has just rolled out the official version of PwnageTool 4.2, which incorporates the new kernel based exploit to create full untethered iOS 4.2.1 custom firmware files. PwnageTool is a freeware that creates custom IPSW to jailbreak your iPhone, iPad, iPod touch and Apple TV, preserving your iPhone baseband to make you able to unlock your device with Ultrasn0w tool.