My personal favorite of the ones I own is Annick Goutal La Violette. This is sweet, candied, and has a spicy rose note.
One that I do not own (but only because I can't justify buying it when I have so many other violets) is Santa Maria Novella Violetta-- Aedes in NYC carries it if you can't find it elsewhere. I got a sample at the store last year. If I could own only one violet, this would be the one.
Also good are:
• Berdoues Violettes de Toulouse. this comes in the Edt and EdP; the latter is colored deep purple and is longer lasting; the former is very light and nice for wearing when going to sleep, or spraying the sheets. I got mine at beautycafe.com. Berdoues has recently come out with a few new ones. Violette Cherie is extremely sweet. I have not yet tried Violette Divine. see:
• Borsari Violetta di Parma-- but I do not prefer this one. Maybe I ought to test it again.
• L'Artisan Verte Violette has an iris note that I do not wear well.
• Penhaligon's Violetta is quite green. I wear this one least often, really have to be in the mood for it.