Tier 1 is often used interchangeably with the Bulge Bracket in investment banking. Therefore, banks in this tier would include all those that work in the largest markets.
In general, there is no defined list of banks operating within the Bulge Bracket, though the following banks are most commonly associated with it:
Bank of America, Barclays, Citigroup, Credit Suisse,
Deutsche Bank, Goldman Sachs, JPMorgan Chase, Morgan Stanley, UBS