Everyone knows what they taste like, but are limes good for you? There are two ways to answer this question. If you're looking at how much antioxidants are in a fresh raw lime, the answer will be no. With an ORAC value that is lower than almost every other fruit tested, it's clearly a loser. But one has to dig deeper to understand the more accurate answer.
For starters the test excluded the peel or skin, which typically we don't eat. Although we don't know the ORAC of the isolated peel, based on the patterns seen across the rest of the plant world, we can conclude it likely has exponentially higher concentrations of nutrients than the pulp inside the fruit (which the test represents). Second, much of a that pulp is fiber which is nutritious in its own right, but the fiber of any plant is not a source of antioxidant activity (or very little). If you remove the pulp and just test what's left, you get lime juice, which does achieve a much more respectable ORAC value of 823. Nothing to write home about, but it is 10x higher and probably represents how you consume it - by squeezing out the juice for your drinks and desserts.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010