Handguns: Glock, Ruger (revolvers).
Semi-auto rifles: Stag, Colt, Arsenal, Izhmash
.22's: Marlin
Bolt guns: Savage
Shotguns: Remington, Benelli.
Not to say I own all of those or won't consider anything else, but those are just the ones I tend to think of before any other when looking for a gun in that category. If I start wanting a particular rifle, then obviously I just want that one. But if I am thinking "Man, I kinda want something in .270", I'll go straight to Savage's website.