I carry from day to day:
-PenFed Platinum Cash Rewards (only for 5% gas)
-Amex Blue Cash Preferred (only for 6% groceries and gift cards)
-Chase Sapphire Preferred (2% restaurants and hotels, better than Fidelity Amex, cause I can redeem any amount)
-Discover More (for rotating 5%, although this quarter it should stay home for online shopping)
-Chase Freedom (for rotating 5% categories)
-Citi Dividend (for rotating categories, electronics stores like GameStop are 5% this quarter, sweet)
-Fidelity Amex (for 2% anywhere I can't get better cash back)
-JCB Card (for 1%, where i can't get better cash back but doesn't take Amex)
-Paypal Business Debit (for 1% on the occasional situation that I can use debit but not credit cards)
-Citi Forward (Thank You points don't do it for me, but the 0% promo apr comes in handy for large purchases I can't PIF)
I choose these cards based purely on maximum cash back value. At home I keep on hand the rest:
-DCU Visa (love DCU, but lackluster rewards keep this on ice, and open only to get free EQ FICO with my checking account)
-US Bank Flex Perks (my 1st failed attempt to get the Cash+, just charge some utilities on it to show use for possible upgrade later)
-US Bank Cash Rewards (my 2nd failed attempt to get the Cash+, this one mostly languishes with its 1% in the sock drawer
-Amex Green (for stuff I want purchase protection on, but don't use it much otherwise. Was planning to switch to the cheaper Zync, but.....
. Now I only keep it to have a charge card in my credit mix).
-Barclays US Airways Card (for the 40k sign up bonus only, and paypal transfers since they earn miles and Barclays doesn't treat them as cash advances. Getting closed come april).
-1st Financial Bank Card (only cause its my longest account, member since 2004, and only card that gets no rewards, or else it'd be shredded long ago. Once every six months for a cup of coffee at Wawa, and that's it!)