More Sex is Safer Sex! $5.99
In the spirit of the much better Freakonomics, Steven Landsburg's More Sex is Safer Sex: The Unconventional Wisdom of Economics uses the tools of economics to look at everyday issues much more interesting than the Laffer Curve.
At the very least, this will give you something to talk about at cocktail parties, at 77% off the cover price. Many of Landsburg's arguments have holes in them, and the somewhat slipshod format makes me think it may have been rushed out to capitalize on the recent popularity of "pop econ" books.
But for $5.99, it's a good gift for the intellectual/economics buff in your life.