I love lemon sorbet or granita. Here's a standard recipe. The recipe has a note about sugar amounts- I like it really tart and tend toward less. Adjust to taste. For a smoother more sorbet-like consistency, try substituting 1/8 cup of the water- use vodka instead.
If you were ever wondering about my icon, it's Masami Teraoka's 31 Flavors Invading Japan (woodblock print 1979)