Here is a low carb margarita recipe from one of my low carb friends. I haven't tried it yet but plan to this summer. All the other recipes this lady has given me have been a hit so I am hoping this will be too. I just bought a Cuisinart ice cream maker and am thinking I could mix this up in there.
The BEST one I've made is to take a diet Mountain Dew (which I normally hate btw) and pour it into a ziploc bag, seal, lay flat and freeze until pretty solid. Then break into chunks, throw in the blender with the juice of 1 lime and a little orange DaVinci's (or a drop of your orange extract perhaps) and your tequila. Blend away!
Makes a nice slushy yummy low-carb margarita.
In the summer I pretty much always keep a bag or two of that frozen Dew in the freezer - great for "spur of the moment" margarita cravings.