I've kept bedding begonias, and also angel wing types, easily and successfully, sometimes for several years in a row. Last year I kept an annual salvia "Victoria Blue" (and I was surprised, I will admit). Calibrachoa usually makes it until late February then dies -- I don't use grow lights so I don't know if that is a light issue or just the nature of the plant. I've overwintered standard petunias, though. Geraniums are easy, even in the north window that I kept them in. There have been a few others that were fillers in the pots when I bought them, that I don't know what they are but they did well.

I usually just overwinter them in the pots they spent the summer in.

You can only overwinter plants which are perennial in their natural habitat. True annuals, by definition, will die over winter. As long as the plants you use are perennial you stand a fair chance of keeping them going.

It's late now but coleus is a good candidate for overwintering. Cuttings do well with some varieties easier than others. I wouldn't do marigold unless I had some very unusual seedling. They are easy to start from seed. Petunias have gotten a little pricey so I did try one very good performer but it didn't succeed. You can do them from seed and I did get some good results from collected seed off the fancy varieties.

As the overwintering prospects grows over the years of plant collecting, I've narrowed down what I would bring in. There are a lot of houseplants like marantha and rhizomatous begonias that are better suited for overwintering results and make a better impact in the garden because they come out of wintering looking good or they are quick to recover their size. Abutilon, tender salvias, Coprosma, Persian Shield, plectranthus, all kinds of geraniums, muehlenbeckia, tender ferns, etc - a lot of the expensive annuals that don't come in packs do well. Of course you can't save them all though you may try.

Some I don't do because the recovery time is too long- anything with gray needles like rosemary, curry, tender lavender, mandevilla (takes all summer to recover).

Keep in mind my setup is light shelves in the basement. I don't have sunny windows for things like hibiscus.