a coin glued to concrete...and the fun begins...people try to pick it up

Yes!, of troy! But even more fun here at the shore is the old string-on-a-dollar-bill gag on the boardwalk! Heres' how it works: You punch a small whole in, usually, a dollar bill (but you can use a $5 or $10 if you're that brave!) and tie a sturdy, long string onto it (invisible fishing line works best). Then you find a nice bench on the boardwalk, lay the bill out, and let the string drop through, along the crack in the boards...and, when some unsuspecting passerby ecstactically reaches down to pluck up their newfound treasure, you give the string a good yank and the bill dances away... And with all the foot traffic there's usually a good twenty people or more to laugh at the poor victims's embarrassment!
But, the more classic approach (and probably safer in this day and age when people seem to be a lot less good-natured than they use to be) is to go UNDER the boardwalk, slip the bill through the crack, and yank it back down through the crevice just as the unsuspecting victim is about to pick it up! This is hysterical when viewed from the top, the stuff that Candid Camera legends were made of! So remember, of troy, if you come down here to the Wildwood boardwalk, don't try to pick up any bills!