I use the HSBC World Elite as my backup card to the BA AMEX. Although AMEX is widely accepted (more so since they capped the interchange fee), there are still many times in which it is not and having this card allows me to direct all spending onto a rewards card that earns Avios (I believe it is the best non-AMEX earning rate you can get).
Also the Amazon voucher conversion option was useful this Xmas (They also have Debenhams, John Lewis, Argos, etc)