I would have to choose either the clawshots from SS or the fire rod from ALTTP. How cool would it be to be able to shoot fire! But maybe I would choose the spinner or the ball and chain from TP... There are just so many cool items from the LoZ series to own that I can't pick just one!
I'd either pick the Beetle or the Clawshots. My problem with the Clawshots is that it would be difficult to grab on to things in the real world. I'd probably choose the Beetle. It would be very useful.
If only the Hover Boots from OOT went a little farther then 3 steps that would be awesome. But even with limited range they would still be pretty fun! Imagine stepping off a cliff and then just floating there for a second before you rush back to ledge! The Fire Earrings from SS would be very handy as well considering how often I seem to burn myself while cooking.