Once again, I can't use these card efficiently cos of  my difficulty hitting my minimum spend on my 2 UOB credit cards. But they may be useful for you.

These are good stand alone credit cards, meaning they don't tie in with any bank accounts to give you better interest rates. (Except the BOC Family card but... more about this below)

A top stand alone credit card would definitely be the Citibank Cashback card.
Pros
Savings of up to 20.88% at Esso, up to 20.8% at Shell and 8% cash back at all other petrol stations
8% cash back at all supermarkets and grocery stores worldwide
8% cash back at all restaurants, cafes, food and beverage outlets globally
8% cash back on Grab rides 

10% rebate in terms of Citi Rebate when spending at Starbucks
Citi Rebate has no expiry, but can only