US, China, Japan, Germany, now India, UK, France and Italy.
I saw India just put their first, Indian built, aircraft carrier to sea. They already are a nuclear country.
These rankings are Nominal GDP where UK and India are close. As far as purchasing power parity India's economy is triple that of UK. China has actually passed USA in GDP PPP, as far as pure wealth (Nominal GDP) US is still the top economy. That may change in 20 years.