My quest for a favorite margarita recipe might be over with this find from Epicurious. The special ingredient here is agave nectar, a sweetener similar to honey, except that it is vegan and will actually dissolve in cold water. Margarita recipes with agave nectar seem to skip the Triple Sec and the salted rim. Alternatively, you could salt half the rim.
This margarita lets the tequila taste shine through, and 100% agave tequila is recommended. I've found agave nectar at Local Harvest Grocery and Whole Foods.