AMEX SPG and AMEX Asiana BofA are my main cards.

When they don't take AMEX, my favorite card is the Fidelity Visa, 1.5% cashback into your Fidelity account. I tried the Chase Freedom with 3% back on the top three and it was too much work carrying different cards for everything.

For gas I use my Penfed 5% rebate card. I do have the AMEX SimplyCash which also gives 5% but I've had the card for almost 2 months and have yet to see the rebate. CS states that it takes a while for the rebates to kick in, but my Penfed rebates kick in automatically every billing cycle.