Sheesh...Ok, I'll play.
Beretta: Legendary maker. The oldest marque in the firearms world. Make very nice medium-high end (not luxury, but very nice) shotguns. They also make a well-regarded line of autopistols, including the current US military sidearm. Their most prevalent pistol designs are a bit dated now, but they're trying to make some progress with some slightly more modern lines.
Bennelli: Subsidiary of Beretta. Makes high quality (not luxury) shotguns.
Browning: Classic name. Now affiliated with FN. High quality rifles and shotguns, primarily hunting/sporting arms. (There are many classic guns with the Browning name attached which are not made by the current firm.)
Colt: Classic marque. Mostly good production values, though they've had rough patches. Almost ceased to be a civilian arms manufacturer in the last few decades, concentrating almost entirely on military contracts, but now making the effort and putting out some nice pistols in the civilian market.
Glock: The ubiquitous semi-auto pistol of the modern age. Good quality, good price. It works. No "frills," almost anti-aesthetics, but if you can't get it done with a Glock, that's not the fault of the gun. The base-line choice for law enforcement and action/practical competition shooters.
HK: Somewhat a niche-market item in the civilian world. Very expensive guns with a lot of cachet. Most shooters tend to find themselves asking exactly what these expensive guns do that's any bit better than any dozen other guns they could have bought. Their military style guns are also high on "cool-factor" but tend to be a bit quirky. They did make THE dominant submachine gun of the end of the 20th century (MP5). Now that the age of the sub-gun has passed, that just adds to the legend.
Kahr: Solid quality concealable pistols. Good value, reliable, concealable.
Kel-tec: Innovative designer. Very fond of cheap-feeling plastic, but their designs are pretty unique and interesting. Masters of "vaporware" -- advertising things and creating massive interest in products that take years for anyone to get their hands on. (KSG, FRB) Their tiny hide-out pistols have become a sort of industry standard, though, for inexpensive conceal-ability.
Mossberg: One of the most prolific manufacturers of civilian arms. They make solid, but inexpensive arms for the common man (uhhh... the WalMart Shopper, TBH). Also make the primary military issue shotgun (590). Their Model 500 pump shotgun is just about equally popular with the old standby Rem 870. They also make rimfire rifles, centerfire bolt-action rifles, now a lever-action as well. Some of their recent design versions tend to be very blatant appeals to the "video-game fanboy" set. Strange things like shotguns with top-handle grips or fake silencers, "tactical" lever-action rifles, .22 rifles with enormous muzzle brakes. Moronic, but it brings in the cash, I guess.
Remington: Grand old name in American firearms. They make a number of rifles and shotguns mostly intended for the sporting market. They've fallen on troubling times recently since their conglomeration under the Cerberus company. Quality is said to be off.
Ruger: Good quality arms for the common man. They've always been innovative and interesting, though their designs sometimes tend toward "bulk=strength." Hard to go wrong buying a Ruger. Might not be the flashiest, or the very smoothest, but solid and reliable. Hard to classify, though, because they make so many different things. A Ruger No.1 and a Ruger P85 almost are hard to imagine coming from the same company, but they did.
Springfield Armory: Pretty good quality makers of M1A (M14 clone) rifles, 1911 pistols, and importers of the "xD" line of polymer autos from Croatia. Very decent quality. Good customer service. Good support to the shooting sports, too!
Savage: Used to be the poor man's Remington. They've put on an intense push in the last couple of decades to build the brand and now produce rifles that many feel are every bit as accurate as a Remington -- and probably more. They build an affordable off-the-shelf rifle that is competitive in F-class bench-rest competition. That's impressive. They will sell you a quality .338 Lapua. That is impressive, too! Their rifles are interesting for incorporating the "AccuTrigger" which makes for a safe, light trigger without gunsmith work. Their primary rifle line also is interesting for the barrel-attachment system which makes swapping barrels/calibers something that the average owner can do at home.
Sig: Another high-quality maker, primarily of pistols. Their pistol designs are dated now, still clinging to the old DA/SA firing system, but they're still pretty popular. Their newer designs have not been all that well received, compared to the legendary status of the old models. Folks tend to either love or hate Sigs, depending on whether they like the chubby grip, high bore axis, and oddly placed controls. They're also making some waves with their Sig556 line of semi-autos, which are a bit evocative of their legendary 20th century assault rifles.
Smith and Wesson: Lots to say. Primarily known as a revolver manufacturer -- and, any more, "
THE" revolver manufacturer. "Quality" is hotly contested. Some love them. Some won't forgive them for not being the S&W of the 1900-1950s era when they were GREAT. They went through a couple of ownership changes in the last couple of decades which saw an unfortunate political deal with the Clintons and ushered in the age of the "internal lock" which many manufacturers now incorporate. They now use some modern machining and manufacturing processes that some people really don't trust, but 98% of the time, their guns work and work well. They also make the M&P polymer autos -- the only gun to REALLY begin to eat Glock's lunch. Great auto and probably the pinnacle of polymer service sidearm, for today. Also making one of the most well-liked AR-15 clones.
Taurus: Generally decent quality down-market handguns. Legendary BAD customer service, and semi-legendary rate of putting out "lemons." HOWEVER, if you get a good one, they tend to really work very well. Some folks who've owned them have sworn off them. Some owners are intensely loyal with nothing but good experiences. You roll the dice, you take your chances.
Wilson Combat: One of the two most prolific "TOP End" 1911 makers. Branching out into some rifles as well now. Extremely accurate, quite expensive, semi-hand-made guns. Bill Wilson founded IDPA.
Cz: Very classic European maker. Make some TERRIFIC rifles, including an interesting assault rifle that many people feel is what the AK
should have become. Their flagship pistol is the classic CZ75 and its derivatives. Interesting gun, very pretty, very accurate, rather "European" in its trigger mechanism. Many die-hard fans. Probably the most unsung and worthy European arms brand.
FNH: Makers of military hardware, including many of the assault rifles, machine guns, and automatic grenade launchers our troops use. Also well regarded for the FN-FAL rifle (the "
Right arm of the free world") -- the direct competition to our M14 back in the day, and felt by some to have been the better rifle. Now they are affiliated with Browning and Winchester. Make a product-improved version of the BAR rifle, the FNAR which is very accurate. Also making a series of service style autopistols which are well regarded.
Nighthawk: VERY high quality niche-market 1911 maker.
Les Bear: The other of the most prolific two semi-custom TOP end 1911 makers, along with Wilson.
Kimber: Responsible largely for the resurrection of the 1911 in the US. After a fantastic run of making the 1911 everyone wanted, they've fallen into some bad times and now their name is tarnished in that area. Making the interesting "Solo" carry gun...similar to a Kahr. Also making a very nice line of bolt-action hunting rifles.
Olympic Arms: Uh...AR-15 maker. Not well regarded these days.
STI: Fantastic up-and-coming pistol (and now rifle, too!) manufacturer, specializing in 1911 and 2011 style pistols, primarily for the competition crowd, but making lots of serious-use carry guns as well.
So... you want to know anything about the 10-20 other makers you didn't think of?