Cosmos' are pretty bombproof. Zinnias, too.
I didn't have good luck starting either of them outdoors from seeds...but I did have a few Cosmos show up suddenly at the end of the year. Maybe I'll buy actual plants this time around.
And it's *just* possible that a few of the bulbs I planted survived the dog's handiwork. I'm not sure he dug every one up. Maybe I'll have a few surprises in early spring.