 
iH8Sn0w has released Sn0wBreeze v2.9.8 with iOS 6.1 support for iPhone 3GS, and A4 devices including the Apple TV 2.
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What is New?
● Added 5.2/6.0.x/6.1 untethers provided by evad3rs
● Added iOS 6.1 support for iPhone 3GS, and A4 devices.
● Fixed Hacktivation issues on 6.0.x.
● Fixed some iFaith mode bugs.
(I  should note AppleTV 2 stuff such as XBMC is currently broken. So you   may want to hold back on updating until your favorite tweaks are  updated  and available.)
Downgrading:
Use iFaith mode after  selecting/downloading the appropriate IPSW for  your device. You will  then be prompted to browse for SHSH blobs for the  IPSW you have  selected. 
Remember to enter a PWNED DFU state with sn0wbreeze's iREB  button in  the top bar of sn0wbreeze prior to (SHIFT + Restoring) the  custom  signed IPSW!
A5(X)/A6(X) Support?:
As stated  many times in the past, sn0wbreeze cannot be updated to work  on  A5(X)/A6(X) devices until a low level exploit in DFU or iBoot is  found  and made public.
A5(X)/A6(X) Baseband Preservation/Hacktivation?
For  those running A5(X)/A6(X) devices and need to preserve your  baseband,  there is nothing you can do at the moment. For those wanting  to  hacktivate, the only advice I can give is to buy the carrier's SIM  (the  one its locked to obviously) on ebay. The SIM does not have to be   activated with the carrier to activate the phone.
Known Bugs/Issues:
● Windows 8 users currently need to use 
this workaround to run sn0wbreeze.
● First boot on an AppleTV 2 for 5.1/5.2 firmwares has funky glitches. Should be fixed by updates pushed via repos.
● iPad baseband will fail to flash on iOS 4.0 --> iOS 4.2.1 restores.
● iPod Touch 2G 4.x.x restores fail (fix coming soon).
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Download
Sn0wBreeze v2.9.8 .