Half Table Console
Unless you want to do a lot of sawing, the likely candidate for this project will have an extending mechanism to accommodate a leaf. (Hint: Any damage or wear -- a missing corner block, a major crack -- drastically reduces table prices at flea markets.)
Simply unscrew the extension mechanism from the bottom of the table, sand the table, then prime and paint it.
Nail or screw a 2-by-2-inch piece of wood to the wall at the height of the tabletop, so that the edge of the table rests on the wood support.
For extra stability, screw through the top of the table to the wood support; fill the holes with wood filler, and paint over them.
At last, you'll have a place for your keys.