This may be old news, but I haven’t seen it around before.
You can get a $10 Amazon credit just for adding a Citi Card to your account and making it the default 1-Click payment option.
I logged into my Amazon app on my iPhone and saw a banner with the deal. I don’t know if this is targeted or open to anyone, so YMMV.
In the past, I have heard of others getting a $10 credit if they use some of their ThankYou Points to pay for their purchase, but this is the first I have seen $10 just for using your card.
It looks like you do, in fact, have to use your Citi card for a purchase to get the $10 credit.
Click on the button then enter your card number. Choose the billing address and voila!
Must be used by January 16, 2016.