I hate pennies so much right now, because I've been doing this with them for the last three days:
That is my upstairs bathroom. The room has been a disaster since I bought the house 2.5 years ago. It finally got to the point where it wasn't even usable, so I'm ripping the whole thing apart and redoing it.
I have a bit of an obsession with copper. I have to resist the urge to buy anything made of copper, or that is copper plated. So I looked into some sort of copper-colored tile, only to discover actually pennies are a cheaper option(~$2.95/sq ft at this packing density).
With a bit of luck, I will be done with the last corner tonight, and can start sealing them with high-build polyurethane tomorrow.
In addition to the floor, new wainscotting is going in, as well as anaglypta wallpaper. I've also stripped the paint off the exposed copper water lines and given them a coating of high-gloss clear. The clawfoot tub will be getting restored & upgraded with a shower, and the toilet & sink will be redone with all new guts as well.
Hopefully by the time I'm done this project it will have finally gotten warm enough I can go out and work on car stuff again.
EDIT: I forgot to mention, none are visible in the photos, but there are several easter eggs being hidden in the floor, including an entire row of wheat pennies, a british penny(which required trimming the pennies around it to make it fit), two bahamas pennies with the pigs facing up, and (if I can find all the right years), 36 years of pennies in chronological order(for my age).