Not like Halo, or Doom.
Anyways
Konami
Toaplan
Capcom
Because all good stuff (CAVE, Raizing/Eighting, and Treasure) branch off from these. Dunno about Capcom, though the 194x series was great. So was Progear, though that was mainly CAVE...
(Wonder how this thread will go... If there is another thread on this, apologies... It could be a version 2.)

