Loaded up my PS1 emulator and first games I saw were a couple of my favorite games as a kid. Nowhere near the levels of the Metal Gear Solid's or Final Fantasy VII's of the PS1 era, but as a kid, I loved these games. It was Croc: Legend of the Gobbos and The Emperor's New Groove. No idea why I loved them so much as a kid lol but they were made by the same studio, Argonaut Software, or Argonaut Games as they rebranded by 2000. I wondered what happened to them and apparently they went defunct by 2004 :(

Made me wonder, what are some other video game studios we loved that just don't exist anymore?

I decided to make a top 5. My first choice is Argonaut Software, but I also loved

Ensemble Studios (I would've chosen Westwood Studios but I prefer AoE over C&C)
Acclaim Entertainment (specifically Acclaim Studios Austin where I remember them as Iguana Entertainment)
Neversoft (pre-Guitar Hero days)
And of course, Midway

What are yours? 

Feel free to name as many studios as you'd like. 

Pandemic Studios stands out to me. The first two Battlefront games are classics.

Pandemic, the Mercenaries games were some of my favorites as a kid. Ensemble is a good one too, I loved the first Halo Wars game. 

Blizzard.

Acclaim, they made some duds, but Acclaim and Rare kept Nintendo afloat in between first party releases during the N64 days.

Konami.. RIP 2015.

Rare

That one hurts deep

My childhood favorites;

LucasArts (Grim Fandango, Monkey Island)
Sierra (Kings Quest, Space Quest, etc)
MicroProse (Civilization, Transport Tycoon, Grand Prix series)
Bullfrog (Populous, Theme Park, Dungeon Keeper)

Squaresoft
And Konami I guess, if we want to say they dont exist no more.
I also had a soft spot for Visceral Games,