PwnageTool Bundle for jailbreaking iPhone 3GS (old bootrom) on iOS 4.2 Beta 2 has been released by msft.guy.
You can use this bundle with existing version of PwnageTool to create custom firmware files which are jailbroken and hacktivated for iPhone 3GS.
But as always, this bundle is meant for iPhone 3GS with old bootrom only. Those of you who are with new bootrom will have to wait for SHAtter exploit based PwnageTool or GreenPois0n jailbreak tool, both of which are expected to release soon.
Unfortunately though, Cydia is currently broken on iOS 4.2, but msft.guy has released a patched version of both Cydia and MobileSubstrate which you will have to install manually. You can download this patch from here.
To try out this bundle, simply download the latest version of PwnageTool bundle for iOS 4.2 beta2 from here, and then follow the complete step by step instructions posted here for patching PwnageTool 4.0.1 so that it works with iOS 4.2 Beta 2.
NOTE: I haven’t tried this latest bundle, and cannot guarantee that it works. Proceed at your own risk only. We are not to be held responsible for any loss of data, or malfunctioning of your iPhone.