This is nothing new, but just wanted to share a very effective exercise that I throw in now & again with some good results. Basically just a variation of Farmer's walk:
I just walk a set of dumbells up the stairs at the office. Nine flights x5 with 14kgs in each hand is a great, intensive 20 min work-out for me. (I personally take the lift back down, as I have knee probs which the descent aggravates).
I like it as hits every major muscle group as well as heart & lungs, and is very much in the X-Fit "for time" mentality, as well as easily scaleable. And it is also a good one when you're travelling and the hotel has a poorly equipped gym, & you could even substitute your case/backpack for the dumbells. Finally, it is worth doing to see the faces of ur colleagues as they see you preform some crazy exercise as they're coming back from lunch