Stuxnet / mrxnet.sys / mrxcls.sys
This story: http://krebsonsecurity.com/2010/07/experts-warn-of-new-windows-shortcut-flaw/
suggested this new rootkit has code which is looking for Siemens WinCC SCADA system. MS's writeups (http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=TrojanDropper%3AWin32%2FStuxnet.A&ThreatID=-2147331492) contains no information to that effect.
I'd like to get a sample because this is going to turn into a big ol' FUD fest where people use it to claim that people are hacking the power grid etc.