In order, It's Sierra, Interplay, Lucasarts, EA, and Valve. I never sell games, and the largest portion of my collection is made up of PC games, which go all the way back to my early childhood. Because of that, Sierra and Interplay, which were huge publishers in their day, make up the majority of my collection; Lucasarts fills in a bunch because of how much I love Star Wars, EA is there because I've been buying games from them my whole life, unlike Sierra and Interplay, neither of which exists anymore, and Valve is there because I, like most PC gamers, have most of their back catalog sitting on my hard drive.
Edit: I forgot Square Enix was a publisher, and not just a developer. I've probably got more games published by them (or Square or Enix separately) than I do Lucasarts, and almost definitely more than I do from EA.