For shoppers of Amazon, icici amazon credit card is best. As it is totally free and you get real cashback instead of points.
For prime user you get 5% in a normal day for any amount you shop, that's really great. And in sale time also generally you get 5% discount + 5% unlimited cashback thats more than 10% discount limited upto some amount.
In other also 1% cashback is there.
It's very easy to get also.
So what else you need.
HDFC millenia is also a decent option where you get 5% cashback on 5% Cashback on Amazon, BookMyShow, Flipkart, Myntra, etc. But the cashback is capped to 1000 per month