RT Jailbreak Tool by Netham45
To use:
1) Double-click runExploit.bat
2) click 'YES' on the UAC prompt that opens
3) Press 'Volume Down' when it asks you to
That's it!

To use Startup:
Put any files you want executed when the script successfully jailbreaks into the 'Startup' folder.

See http://forum.xda-developers.com/showthread.php?p=36529478 for more information