For general product line diversity FN is pretty hard to beat. They make everything from pistols to shotguns to .50 caliber machine guns. If they don't make the particular type of platform you're after, you probably don't need it.
Most of my collection is Colt, but Colt decided to stop making Pythons, Anacondas, and Troopers, which is a damn shame if you ask me.
I would probably move to another planet or start making firearms myself to offer an alternative to a state arms corporation. Life's too short not to be able to get the toys, ahem tools, that you want.
Remington for bolt action rifles and shotguns. Great rifles for very reasonable prices.
Winchester for M70's. Buttery smooth.
Colt for pistols, revolvers, and carbines. Nothing like a Colt for quality American workmanship at an affordable price.
FN for SCAR's. Who doesn't love an 8 pound .308?
SA for 1903's and M1's. Who's bright idea was it to shut down SA, anyway? Someone should have been shot over that, that's all I'm saying.
SEI for M14's. Since the rocket surgeons shut down SA, somebody has to keep the beast alive.
KAC for SR-25's. Stoner had great ideas and his buddy Reed maintains his legacy.
Ruger for GP100's. If it ever fails, not that it will, you can still beat someone to death with it.
There's no way I could live without those brands. I might as well move to Mars.