The Capital One Quicksilver Cash Rewards Credit Card is a good all-around card that offers a variety of benefits, including a welcome bonus, a flat rewards rate, no annual fee, and a good introductory APR offer.
While the individual benefits may not be the best in their class, they are still valuable and make the card a worthwhile option for many people.
I personally bring my Quicksilver everywhere in case as a back-up card.