A street samurai is someone who uses gear and a code of street honor. (Note that it isn't necessarily what one would call "honorable", just like the samurai of feudal Japan's code of honor is very different than what one normally thinks of as "honorable," they both honor specific codes of conduct and thus have honor for those specific codes.) The gear is typically composed of lots of firepower (automatics, shotguns, heavy weapons) and cyber- and bioware.
The sam is typically heavily augmented, so much so that his Essence rating is often 1 or lower. Typically can take a lot of punishment, and dish it out, so they are often combat monsters. Note that in Shadowrun, the combat monster is a support character. The other characters, those with the skills needed to infiltrate and/or bypass security and achieve the objective, are the ones that get the job done. Optimally, they do it without alerting security to their presence. Unfortunately, the optimum result does not happen as often as one would like. So, that's when the street sam pulls everyones butt out of the fire.
The side effects of low Essence can include quite a few neurological and behavioral disorders. Including, but not limited to: depression, sociopathy, excessive aggression, moodiness, cyber-psychosis, and being a crappy friend.
