To date this one is my favorite, and it may simply be the situation I'm stuck in with it.http://www.bleepingcomputer.com/virus-removal/remove-ice-cyber-crime-center-ransomware
System came to me with a variant of the ICE Ransomware infection. I pulled the hard drive, slaved to a Malware removal VM, and away I went. I removed 28 infections on the first pass. The system could be clean at the moment, but it's hard to say because the OS has been damaged a bit.
The buggar with this one for me has been that the client has previously ran the free version of HitmanPro, and so it couldn't be used to remove the infection. This left me with other AV tools, which have not seemed to work as well.
Ultimately all PE/Rescue CD's have failed to solve the issue. This is a fun one! Going to really hammer it today, as I have more time to focus on it.