Potatoes naturally grow underground in dark, wet soil. For this reason, you can grow potatoes in an old wine barrel by planting them in layers. All it takes is planting seed potatoes, or pieces of seed potatoes, at 6-inch intervals covered with soil in the barrel. This is ideal for a gardener with limited space and can yield dozens of potatoes. It is important to plant the seed potatoes after the last frost, so they are not destroyed by a cold snap.
An old wine barrel can be easily converted into a coffee table. The quickest way is to clean it (and sand it and finish it, if you want a cleaner look) and flip it over to use the bottom as a table surface. You can decorate the barrel by painting it, or using a thick lacquer to smooth out the surface. You can also saw the barrel in half, flip it over and add legs to make it a more formal table.
This is a similar idea to growing potatoes, but with other plants. Saw a wine barrel in half, and drill holes in the bottom of each half. Set the barrel halves on the ground and fill with soil and seeds. This works for flowers, leafy greens, herbs like basil or cilantro, and anything else that thrives with a shallow, open bed.