After more than 6 years of trial and error, I now feel comfortable recommending my five favorite really-hard-to-kill plants. These are all sun-loving, NOT water-loving flowers or shrubs that don't require rich soil or any special treatment whatsoever. Water them every few days for a coupla weeks right after you first plant them to get them established, then you should be able to basically ignore them (unless it's super hot with no rain for more than a month or so.) Putting some high-quality, hardwood mulch around them helps allot, too.
So here they are, in no particular order. I can't figure out how to make the pics from our yard post next to their corresponding text, but the pics are (from top to bottom) in the same order as my descriptions. Hope that makes sense.
Plumbago: loves sun but can handle part shade, too. Cover it in winter during hard freezes during the first year. Blooms from late Spring through mid-Fall.
Mexican Sage: grows pretty quickly but can be trimmed back. Blooms early Summer through mid- to late Fall.
Rubber Plant: haven't seen its blooms yet--I think they have small pinkish-white blooms in Spring.
Bicolor Iris: blooms in Spring with white flowers that are sort of periwinkle-shaped.
Rosemary: REALLY does NOT like much water. Besides being a great edible herb, it smells good and blooms small, pale, bluish-purple flowers erratically.