Bitmap Brothers, Rainbow Arts, Team17, SSI, FTL, Psygnosis, Firebird, Sir-Tech.
Squaresoft, ID Software, Valve, Bungie, Looking Glass Studios, Bioware, Black Isle, Namco, Konami, Bizarre Creations, Tecmo, Nintendo, Sega, Capcom, Origin, 3DO, Blizzard, Atari, Don Bluth etc...
+Anything Sid Meier, Chris Sawyer, David Braben.
Some companies have merged with others, these are the companies as I remember them. Any spelling mistakes, sorry!!