I believe Leucojum should be added to this list. It's been the toughest and most reliable of flowering bulbs in our north Texas garden for many years. Forms huge clumps after a few years and blooms profusely for a couple of weeks in early to mid Spring. No pests, no problems, just give a bit of bone meal after blooming and in the early Spring. And unlike so many "snowbells" type bulbs, Leucojum definitely does not get lost in the garden; its bloom stems are up to two feet tall, and covered with flower clusters.