Updated the *standalone* p0sixspwn to v1.0.8. Supports 3GS+ipt4 on iOS 6.1.6. Fixes iTunes 11.1+ crashes.
P0sixspwn can jailbreak iOS 6.1.3, 6.1.4, 6.1.5 and now 6.1.6 devices. There is also an untether package available on Cydia for those currently on 6.1.x but have a tethered jailbreak.
You can find download links for the utility here.