This category, which includes cards that help people save for retirement, college, a car purchase or other goals, has waned over the years as people opted for more immediate rewards. Still standing, though, are the three Fidelity-affiliated American Express Rewards Cards, which deposit your rebates into your Fidelity investment, retirement or college savings account. Four out of the five experts nominated one or all of these cards for their straightforward 2% rebate structure. Stubbs says she's always been a fan of the Fidelity Investment Rewards American Express card "because it offers a straight 2% cash back on all purchases and because it encourages saving. This card is so simple -- no rotating categories, no spending thresholds, no point caps, automatic cash deposited into your Fidelity account and no annual fee."

Upromise World MasterCard from Sallie Mae received three nominations. Rewards can be deposited into the affiliated 529 college savings plan or a high-yield savings account or used to pay off Sallie Mae loans. They can also be taken as cash back. The Upromise pays 5% to 10% rewards when users shop through the Upromise online storefront, and "the selection of merchants is actually decent, and includes Wal-Mart, Target and Macy's," Sekar noted. "It also earns 4% back on eligible restaurants, 3% on Exxon Mobil gas, 2% at movie theaters and 1% elsewhere."

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"This can be a great way for parents and grandparents and other family members to team up and leverage their spending to help save for college," Woolsey added.

Honorable mention: GM Credit Card, which Papadimitriou called "a great option for anyone interested in purchasing a GM vehicle, as it does not charge an annual fee and offers 5% cash back on all purchases, redeemable towards a GM purchase."

Liz Weston is the Web's most-read personal-finance writer. She is the author of several books, most recently "The 10 Commandments of Money: Survive and Thrive in the New Economy" (find it on Bing). Weston's award-winning columns appear every Monday and Thursday, exclusively on MSN Money. Join the conversation and send in your financial questions on Liz Weston's Facebook fan page.