This dessert is a refreshing way to conclude a spicy southwestern meal. For a festive note, dip the rims of frozen Margarita glasses into water and then into a bowl of sugar. Attach a lime slice to the lip of the glass and fill with sorbet.
Stir water and sugar in heavy medium saucepan over medium heat until sugar dissolves. Increase heat and bring to boil. Pour into medium bowl. Mix in lime juice, triple sec, tequila and lime peel. Refrigerate until cold, about 2 hours.
Transfer sorbet mixture to ice cream maker and process according to manufacturer's instructions. Transfer sorbet to container; cover and freeze until firm, about 2 hours. (Can be prepared 2 days ahead. Keep frozen.)
Freeze 4 Margarita glasses for 1 hour. Scoop sorbet into frozen glasses and serve immediately.
Note: If you do not have an ice cream maker, you can turn this mixture into a granita an Italian frozen dessert. Mix an additional 1 cup water into sorbet mixture. Freeze in bowl until semifirm, whisking occasionally, about 3 hours. Cover and freeze until solid, at least 6 hours or overnight. Using fork, scrape surface of granita to form crystals. Scoop crystals into frozen glasses and serve granita immediately.