Are there any discs that a company makes that another company doesn't? Everyone always says that using one brand is limiting but I haven't really seen any molds that one company offers exclusively.
There's a couple I can think (that are different enough from other discs to be mentioned, IMO) of but there may be more that are probably not worth throwing:
Innova: Teebird
Discraft: Predator
Gateway: Sabre
Now, there are other discs that will work for the same slots, but they won't have the same performance as those discs. There may be more, but that's what I got off the top of my head.
As for the OP's question I'll list what are, IMO, the best discs from each company unless there's just a ton of discs in a category from all companies (understableish speed 9 drivers, for example).
Innova: BB Aviar, Roc, Teebird, Gazelle, Eagle, Firebird.
Discraft: Challenger, Banger, Wasp, Buzzz, Cyclone, Avenger, Predator, Force.
Gateway: Wizard, Warlock, Voodoo, Blaze, Spirit
Millennium: Omega, SOLF