At least one day a week I use the Versaclimber for intervals. It's a rarely used piece of equipment sitting among the treadmills and ellipticals Every time I climb on it, people doing their 30 minutes of cardio give me looks.
Of course I'm done long before any of them. The Versaclimber gives me an incredible workout. It's hard. Really hard. After each one-minute interval, I climb down out of breath. But it's also an incredibly efficient workout, much more so than anyone around me. So they can look all they want, because doing what everyone else is doing at the gym rarely makes sense.