Who didn't have a favorite plaything as a child? In fact, many investors carry their love of certain toys well into adulthood, continuing to collect examples for personal pleasure and, sometimes, profit. Rare, antique toys in mint condition are the best investment bet, but realizing returns from what's essentially a hobby takes patience, expertise and money to burn, say experts.

Here's a look at some of the most popular types of toys collected as investments, as well as some that, while popular, are losing propositions profit-wise.

—By Sarah O'Brien & Kenneth Kiesnoski, Specials to CNBC.com
Posted 12 April 2014

The toys bringing in the real money now are complicated mechanical ones dating back to the 19th century, such as mechanical banks. According to Michael Bertoia, owner of family-run Bertoia Auctions in Vineland, N.J., one such antique toy bank sold for $426,000 back in 1998.

Toys mass-produced in recent years carry more value if they are in their original packaging and have never been played with. But it's difficult to predict what will increase in value. Terry Kovel, co-author of "Kovels' Antiques and Collectibles Price Guide," said that some Star Wars figurines that no one wanted in the 1970s are now valuable because so few of them were produced.

What's hot one day might be unappealing to collectors the next. Robot toys made in Japan after World War II skyrocketed in price for a few years — but then collector interest, and prices, dropped off.

"If you're investing a small part of [your portfolio] in a collectible and it gives you joy, that's great," said certified financial planner Clark Randall, founder and owner of Financial Enlightenment. "But I wouldn't count on that kind of investment funding your retirement."

The Cabbage Patch Kids dolls — probably the biggest and best-remembered toy craze of the 1980s — are still popular with die-hard fans and collectors. Some 65 million of the dolls were "delivered" from their 1982 debut through 1990, according to eBay. Cabbage Patch Kids were so iconic and ubiquitous, they even spawned a nearly-as-popular parody: the Garbage Pail Kids trading-card series.

There's still a lively trade in the dolls, particularly on online auction sites, but collectors aren't going to get wealthy; a circa-1984 Cabbage Patch Kid in original packaging with clothes and "birth certificate" can sell on eBay for about $30. Amassing the dolls is more a labor of love than a get-rich-quick (or -slow) scheme.

Transportation-related toys — cars, trains, boats and airplanes — are very much sought after by collectors. Tin wind-up toys are also popular. A windup car or motorbike, ergo, would be especially coveted, particularly if it is antique, undamaged, unchanged and, again, in the original packaging.

"Sometimes it's because the box has great pictures on it," said author and collecting guru Terry Kovel. "Nothing is in mint condition if a kid has played with it, but it can be in excellent condition."

Trading cards have always been popular with both kids and adult collectors. Topps is perhaps the best-known issuer of "bubblegum cards" in the U.S., having inserted baseball cards, the Wacky Packages series and the aforementioned Garbage Pail Kids cards in packs of gum since the 1950s. Vintage baseball cards in mint condition can fetch a pretty penny at auction.

A more recent card-collecting craze is the Pokemon Trading Card Game (pictured), launched in 1996 as a spinoff of Nintendo's Pokemon video game series. Fans not only collect coveted character cards but battle it out in international tournaments.