Answer Products Co.
These folks have been customizing and building fine rifles since 1986. They have a variety of products, including muzzle brakes, exotic recoil pads, scope mounts, and cleaning solutions.

Birchwood Casey
These folks make some great shooting products - targets, wood & metal finishes, cleaning & maintenance. I love their Shoot-N-C targets, myself.

Bore Cote (Firepower FP-10)
Said to remove lead, copper and powder fouling, leaving your gun dry after application. Reductions in fouling are promised, along with increased velocity and reliability of feeding.

Boretech
Bore cleaners, black powder solvents cleaning supplies.

Cleen Bore USA
Gun cleaners and solvents.

Clenzoil
This product has been around since 1948. Billed as a cleaner, lubricant, and rest preventative for all types of guns.

Eezox
These folks make something called Eezox Premium Gun Care, which they say "cleans, lubricates, and preserves firearms." This is a non-petroluem, non-flammable product, and it sounds promising.

Flitz Metal Polish
Flitz offers metal polish, gun/rifle wax, tumbler media, and other polishes/protectants.

Gun Slick
Gun cleaners and protectors.

Hoppe's
Hoppe's gun care products have been around for ages... in fact, the company was founded in 1903. Their No. 9 Nitro Powder Solvent is almost legendary. Targets, cases, eye & ear protection, more.

Invisible Gun
Cleaners without the scent.

Kleen-Bore
This family-owned company has been making firearms maintenance equipment and solvents for a long time now, and from what I've seen, they have some good stuff.

Outers
Gun cleaning supplies and more.

Pro-Shot Products
Pro-Shot has brushes, jags, patches, rods, cleaning kits, bore mops, chamber brushes, bore guides, black powder and smokeless cleaners & solvents, lubes, etc. I have used their jags and brushes with satisfaction.

RB-17 Gun Cleaner
According to their site: This is non-toxic, biodegradable, and all natural. Dissolves rust, copper, lead, brass, and black powder fouling, removes plastic from shotgun bores. Watch your stock - it'll also remove varnish.

Rig Products by Silencio
The Rig brand has been around for over fifty years now. Cleaning kits, rods, accessories, lubes, and cleaning solvents.

Shooter's Choice
Solvents, lubes, rust preventers, degreasers, a variety of stuff for smokeless and black powder guns.

Tetra Gun Products
This company makes a wide array of products for guns, including cleaners, lubes, solvents, liquid blue, rust remover, and cleaning rods & accessories.