During the Act 1 briefing, there is a PlayStation3 on the second floor of the plane.
Go upstairs on the Nomad during the Act 1 briefing to see Sunny unpacking her PS3 and PSP.
During the Act 2 briefing, there is a PlayStation3 on the table.
Next time you send out the MK2, look over Snake's shoulder by tilting the camerahe is using a PlayStation3 controller to control it.
If you use a Sixaxis controller against Psycho Mantis, he says, "What? No vibration!" and the flashbacks show the Sixaxis.
Use the Codec to call Rose during the fight with Screaming Mantis. Campbell will say to switch controller ports. Rose will get mad and say there are not any controller ports because this is on a PlayStation3.