As consumers get smarter about using credit cards, banks have discovered that big cash rebates can drive customer loyalty. If you keep just one or two credit cards in your wallet, consider carrying a card that can earn you as much as 6 percent cash back on eligible purchases. Here are some of our favorites:

Discover® it card

The original cash back credit card has returned with a new look and a revamped rewards structure. You'll still get up to 5 percent cash back on purchases that qualify for Discover's quarterly feature promotions. However, the Discover it Card now features a straightforward, 1 percent cash back on all other purchases. With no annual fee, no foreign transaction fees, and a host of customer-friendly features, this could be the card that brings Discover home to even more Americans.

Blue Cash Preferred® Card from American Express

Our perennial favorite cash back credit card for consumers with excellent credit, Blue Cash Preferred offers 3 percent cash back at U.S.gas stations and at select US department stores. However, your first $6,000 of purchases at U.S. supermarkets earns a whopping 6 percent cash back each year. Rebates of 1 percent apply to your everyday purchases, making this rewards card a solid choice for households with school-aged kids. Terms, limitations and restrictions apply.

Fidelity® Investment Rewards American Express® Card

The lone affinity credit card on the list offers the highest rebate for everyday purchases: 2 percent. Offered through a partnership between Fidelity and a Bank of America subsidiary, this account lets cardholders convert rebates into deposits of $50 or more into a linked investment account at the popular brokerage. If you're not an active trader, you can still get versions of this card linked to a 529 college savings account or to an individual retirement account.

Chase Freedom®

One of the most highly publicized cash back credit cards often gets our attention for offering some of the biggest signup bonuses in the business. Depending on the time of year, new Chase cardholders can earn as much as $100 bonus for adding a Freedom card to their wallets and reaching a spend threshold of $500 in purchases in your first three months from account opening. This card offers an everyday 1 percent rebate and quarterly promotions that bump rewards as high as 5 percent on purchases at participating retailers like Amazon.com, gas stations and restaurants (subject to enrollment and quarterly cap in combined purchases).

Citi® Dividend Platinum Select® Visa®

Citi's own cash back card doesn't seem to get as much television airtime as Chase's. New cardholders can qualify for $100 cash back from Citi after reaching a spending threshold of $500 in purchases in the first three months of account opening. Like Chase Freedom and the Discover it card, Citi Dividend Platinum Select offers its own set of quarterly bonus deals with rewards from Citi earn up to 5 percent cash back every quarter in must-have categories subject to enrollment each quarter (which is easy) and 1 percent on all other purchases. With this card cash back total is $300 per calendar year, excluding the $100 cash back with this offer. See Citi Dividend Card Reward Program Information. With no annual fee and a strong balance transfer offer, this card offers a great way to pay down debt while enjoying everyday rewards.

BankAmericard Cash Rewards™

The BankAmericard Cash Rewards credit card offers 3 percent cash back on gas, 2 percent rebates on groceries, and 1 percent rewards on your everyday purchases. Redeeming your rewards into a linked checking or savings account earns you a 10 percent rebate bonus. Although Bank of America limits its bigger rebates to the first $1,500 in spending each year, you can still earn 1 percent on everything else.

PenFed Platinum Cash Rewards Visa® Card

This credit union Visa card earns a slot on our list because of its 5 percent reward for gasoline purchases paid at the pump with the "Plus" version of the card. You'll need to have a qualifying PenFed Product, for example a money market savings account, or an active checking account with direct deposit ($250 min.) as well as excellent credit and a military pedigree to qualify for this card, designed primarily for families of active service members. If you're not part of the armed forces, you can still gain eligibility for PenFed membership by joining a qualified organization with a low one time fee. The Standard version of the card offers 3 percent cash back on gas purchases paid at the pump with an introductory annual fee of $0 for the first year and after that a $25 annual fee. As a side note fuel purchases for airplanes and boats do not receive cash back rewards with either version of this card.

As always, you'll qualify for the most valuable signup offers if you're switching to a new credit card issuer for the first time. Just remember to pay down your balance each month, or finance charges can eat away at the big rebates you'll earn throughout the year.