IBM's supercomputer, the Roadrunner, which cost something close to $ 100 million dollars.
IBM is a great company of Free Software as a whole and also specifically to the Fedora project, reports that Fedora is used in the test environment with this and other machines.
Roadrunner Name System
Site DOE / NNSA / LANL
Family IBM System Cluster
System Model QS22 BladeCenter Cluster
Computer QS22/LS21 BladeCenter Cluster, PowerXCell 8i 3.2 GHz / 1.8 GHz Opteron DC, Voltaire Infiniband
Installation Year 2008
Linux Operating System
PowerXCell 8i processor 3200 MHz (12.8 GFlops)