Bulge Bracket Investment Banks (BBs) – The largest multi-national investment banks, typically offering a range of services.

JP Morgan, Goldman Sachs, and Morgan Stanley; Bank of America Merrill Lynch and Citi; Credit Suisse, Barclays and UBS.

In-Between-a-Banks (IBABs) – A cultural mix between Bulge Bracket and Middle Market.

Wells Fargo, RBC, and many European, Asian, and Canadian banks, such as HSBC, BNP Paribas, Mizuho, Nomura, BMO, CITIC etc.

Elite Boutique Investment Banks (EBs) – Non-full service firms focusing on M&A Advisory or Restructuring that advise on the same types and sizes of deals as Bulge Brackets.

Centerview, Evercore, Greenhill, Guggenheim, Lazard, Moelis, Perella Weinberg, PJT Partners (formerly Blackstone), Qatalyst, and Rothschild (only in Europe).

Up-and-Coming Elite Boutique Investment Banks (UCEBs) – Deals aren't quite as big yet, but getting there.

LionTree Advisors, Zaoui & Co., Robey Warshaw, Lakeside Capital Advisers, Dyal Co, and M. Klein & Co.

Middle Market Banks (MMs) – Deal sizes generally range from $10M to $500M, and generally work with relatively small, private, local firms.

Baird, Brown Gibbons Lang & Company, Cowen, Harris Williams, Houlihan Lokey, Janney, Jefferies, JMP, Lincoln International, Macquarie, Needham, Oppenheimer, Piper Sandler, PJ Solomon, Raymond James, Stephens, Stifel, Truist, Wedbush, and William Blair.

Industry-Specific Boutiques (ISBs) – Small banks that operate only in a specific industry.

SVB Leerink (Healthcare), Ziegler (Healthcare, Senior Living, and Education), FT Partners (Fintech), Allen & Co. (TMT), Seabury (Transportation/Maritime/Aerospace & Defense), Telsey Advisory Group (Consumer/Retail), etc.

Regional Boutique Banks (RBs) – If a bank operates in only 1-2 locations or smaller non-financial centres and works on very small deals, it’s in this category.

Source: https://www.mergersandinquisitions.com/top-investment-banks/