I originally experimented with barley flour, but have since come up with a rice version that turns out almost exactly like wheat flour tortillas, with only a slight rice flavor. It's an adaptation of a family recipe for French Pancakes, similar to crepes.
2/3 C white rice flour (preferably Asian)
1/3 C glutinous rice flour
1 egg
¾ C water or milk
Blend all the ingredients in a medium-sized bowl. Add a little oil to a well-seasoned skillet, spread it around with a brush or paper towel, and turn the burner on to medium heat. Add about ¼ of the batter, swirling the pan to spread it into a thin circle about 9" across. Cook the first side until the edges lift, then flip it and cook the other side. Leave it in the pan until it starts to brown, flipping every so often. Remove it to a paper towel and repeat. Makes 4 tortillas.
These freeze well, if you want to make a large batch every once in a while for regular use.