"What's your favorite stock?" Many investors, when asked a quick off-the-cuff question like that, may gravitate toward familiar names such as Apple (AAPL) or Facebook (FB). And well they should. Yes, these have been two of the market's best stocks for some time, but they've been so successful for a reason. In both cases, like many other high-profile names, the companies have proven they can sell a product or service.

However, not every great investment is a monster-sized company or a headline-grabbing outfit. Sometimes, an organization that's a bit off the beaten path can bear quite a bit of fruit. It pays to invest in the big boys, but off-the-radar businesses are worth a look, too.

Here's a review of 20 tickers across numerous industries that investors of all stripes should explore. They're not household names, but that doesn't mean they aren't doing well, or that they can't be among the market's best stocks going forward.

Indeed, their obscurity is part of what makes them so compelling.

Align Technology

Courtesy Carrie A. via Flickr

Industry: Dental products

Market value: $20.9 billion

Most people remember Nvidia (NVDA) and Boeing (BA) as Standard & Poor's 500-stock index components that had breakthrough performances in 2017. But many people don't realize that Align Technology (ALGN, $262.00) did even better, gaining 131% to finish second in the index behind only NRG Energy (NRG), by about one percentage point.

You know the company, even if you think you don't. Align Technology is the name behind Invisalign dental braces, which straighten your teeth without using uncomfortable and unsightly metal wiring.

Wall Street's pros believe Align's top line grew 34% in 2017, which should be enough to power a 50% year-over-year improvement in per-share profits. Analysts expect more of the same this year.

While 2018's growth outlook is impressive, ALGN shares aren't exactly cheap. The stock trades at 89.6 times trailing earnings and 45 times analyst projections for next year's profits - and at the same time rivals such as Candid and Smile Direct Club are turning up the heat. This suggests Align shares could be due for some profit-taking. But any dip may be an entry opportunity, because the company knows exactly where it fits into the picture.

"As we transform