PS3 + not "upgrading" the firmware to 3.21
Yeah, yeah, yeah I know.... lots of people saying no one uses OtherOS, who cares and its slow.
Despite the above I quite like the OtherOS feature and I was a little miffed when Sony said they will remove it with the introduction of mandatory "update" 3.21. You can update to 3.21 or face not signing into PSN.
However with a little help from LG5tool.exe you can bypass the firmware update and still sign in to PSN. I'm currently signed in to PSN with firmware 3.15.
Heres some info:
How to Bypass PS3 Firmware 3.21 and Connect to PSN