For my part, my answer would be exactly the same: Zen Flight. This minor monk glyph won't be released until Mists of Pandaria, so you can't find it in game yet. But you can see my monk Krikkit above being all zen-like in the beta.
Wouldn't it be great to float in line at the grocery store, looking all relaxed and glowy? Sure, people would look at me funny, but they do that already -- I have shocking pink hair. Oooh the Zen Flight colors would look great with pink, wouldn't they? Hmmm ... maybe a bit too 80s.
Anyway, I could use it everywhere. Waiting for mass transit? Yes. Crossing the street? Yes. Disneyland? Yes, please.
What spell would you most want in the physical world and why?