This morning I saw the purple car I hit last year while trying to get away from a scary homeless guy. I called that post "The Five MIle Per Hour Kiss." And that would make an intriuging book title. But would people look for MPH or mile per hour spelled out? it probably wouldn't be worth the risk.
Or how about Hailey Lind's Feint of Art? A clever play on "faint of heart." But how many readers ask for it or look for it by using "faint" not "feint"?
Got your own examples?