S&S Munitions is a weapon manufacturer in Borderlands. It is not clear what exactly the two 'S' may stand for. Their weapons tend to have average damage and high fire rate, but lower accuracy. However, they make up for that with increased magazine sizes. S&S utilizes a black and yellow finish on their guns to distinguish them from the competition.
Quotes
"If you find your gun just doesn't hold enough bullets, then S'n'S has the solution: more bullets! All S'n'S guns have extended magazines!" - Marcus' Gun Vending Machine
"The S&S philosophy is: Tech + Ammo Capacity = I win!"
"Reload: (verb) Something you do after your target is dead" - S&S Munition posters seen in Krom's Canyon
^ and at the bottom "Having the largest clip sizes around is just one example of how S&S munitions merge smart design and high technology."
Trivia
S&S Munitions follows a naming scheme based heavily on celestial objects and constellations. For example, the S&S Orion (Orion 'The Hunter' being a well-known star constellation)