I hesitated about including this here since bacopa is not really an annual and it is not even bacopa but, faced with a mass of Cs and no other B that came immediately to mind (apart from bidens which is not really an annual either) I will mention it because it is a common plant these days.
Bacopa was virtually unknown until the 90s when it was introduced as a basket and patio pot plant. A sprawling, low plant with pairs of opposite leaves and small white flowers I have to admit that it seemed about as attractive as chickweed to me. In its favour was the fact that it was pretty tough, tolerated a light frost and it did bloom on and on. It also hung gracefully, though in a sheet that swamped anything in its path, from baskets. It was not something that could be mixed with other cascading plants because its growth was so dense. It would definitely do the job and suppress weeds on the rockery!
As a white-flowered plant for baskets it definitely had merit and a further good point was that the small flowers did at least shrivel and drop off as they aged and went brown so it was always neat. But I found it unexciting. I was in the minority and it has established itself as a popular patio plant. Breeders jumped at the chance of improvement and soon there were (to me) exciting additions.
Soon the plants had blooms (and leaves) twice the size and then there were flowers in pink and lilac. Golden-leaved forms are available too and these are well worth growing since cascading yellow foliage is not that common. Some of these, I suspect, were due to hybridisation with the closely related jamesbrittenia. To clear up the name, bacopa is a water plant while sutera is an African genus. Despite my pedantry I think that bacopa for the plant on this page is so established now that it is best to err on the side of convention and accept that they are bacopa.
Most plants are bought as youngsters in spring. Most are raised from cuttings and you can do this yourself though I find that slightly woody shoots are easier than soft tips in spring. In any case watering must be done carefully or they rot and turn black. Once they have a decent root system they are no trouble at all but they are easily killed by overwatering when young. By late summer you often find that stems have rooted as they grow and these can be removed as new young plants. You can also grow them from seed, sown in spring and these seem to be as good as many cuttings-raised sorts, though the seeds are expensive.
Bacopa does best in sun but will tolerate some shade. In patio pots it may even survive winter if the pots are near the house and protected from the coldest nights.