Either one of the occulus rift or sony morpheus... and the ominu treadmill and six sense controller and a infrared body suit and 4 camera tracking system...
And there you go!
But... while I was watching all these VR world demonstration I couldn't help but to think.. why not just go experience the real world instead... especially when they were talking about excercising on the omni treadmill... I mean for realz?!?!?!
Sure there's some other places and different worlds and scenario's you can't get in the real world... but you know what I mean!