In my mind, Citi is the most generous bank when it comes to credit card. Nowadays, I swipe Citi cards for 90% of my purchases: all grocery shopping and gas refilling go to the Citi Dividend Card for 5% cashback and many other things to the Citi Driver's Edge Card for the also-fat 5% reward (both subject to $300 annual cap). I cannot be much happier when I know I can always get an automatic 5% discount on every single credit card purchase.
By the way, did you know that Citi will actually hand you cold cash without you even swiping the plastic? 
In June 2004, I reported that Citi sent me $150 worth of cash rebate coupons for my willingness to stay with its Credit Protector program. I haven't had a chance to report back on my progress but here is the update:
First, I finally received all rebates in check over an 8-month period. If you read my prior post, you know there are actually 11 coupons totaling $150, and only two can be submitted in a given month. On the other hand, you can submit a coupon with any receipt you have, and, at least in my 11 cases, all rebate submissions are approved. Rebate check usually arrives 2-3 months after you submit the coupon, and during the period, you can check status via RebateStatus.com.
Second, I haven't paid much to stay with the program. Citi's Credit Protector Program charges 49 cents for every $100 balance at the statement date, and you can avoid most of the fees by prepaying all your existing balances a couple days before the statement date. For all these 8 months, I only incurred less than $5 in Credit Protector fee -- all of that is because some purchases just before the statement date show up the same day when my monthly statement is closed. Still, not bad to earn $150 with only $5 cost and a couple hours' work.
What's more, after I deposited all $150 into my bank, I called Citi last month trying to cancel my Credit Protector membership, and I was offered another $50 ($10 x 5) rebate coupons -- less generous, but I figured out it is still worth it, so I stayed. It does not hurt to accept such generousity over and over again, and thank you Citi!
Tips for new comers to the game:
1. Citi usually sends you a $15 check 6-10 weeks after you open your new account. It asks you to join the program by cashing it. Always take it.
2. Remember the Credit Protector hotline: 1-888-592-7344. You will need it no matter you want to cancel or get the fat cash rebate coupons.
3. If you don't use your Citi card much, or can have the discipline (and cash flow) to prepay your credit card balance just before the statement date, you should choose to stay with the program. Call the number and explicitly say you will cancel your membership unless you get deals like cash rebate coupons. You can save both you and the CSR some time by making it clear what you want. After that, be sure to mark your calendar and pay off your balance before statement date every month -- Citi does offer a nice and easy online interface for online payment..
4. If you don't like the monthly hassle to prepay your balance, just tell the CSR you are adament about canceling the membership. I did that for another card and it only takes 5 minutes to end the call. (In this case, whatever the CSR says, repeat your cancellation request.) It's still a great deal to earn $15 by spending 5 minutes on the phone.