Last night's dream was set in some strange, dreamt-up version of New York, possibly after an apocalypse, where there was little or no law enforcement to speak of and the city was torn by constant strife between a few (4 to 7 or so?) colour-coded gangs.
I was a recent initiate into one gang, I can't remember exactly what colour we were but I think it was either orange, purple or red. There was plenty of stuff that went on, but the main part I remember was where myself and another gang member- either a more experienced, tough member or another rookie like me, not sure- had to catch a train to some distant part of the city/other city for some important mission. It started off at a dark, dingy underground station not unlike New York's real-life subways, then became an aboveground train later on.
The people who operated the trains seemed to be the only remaining authority in the city, responsible for keeping the trains running, the tracks maintained, etcetera. They shepherded the gang members (there were a lot of people from different gangs catching this train) and we set off.
My companion and I were nervous, since we were the only members of our gang in our carriage, and it contained a large, boisterous group of the yellow gang, who were bitter enemies of ours (and a bunch of irritating douchebags to boot). However we ended up somehow befriending at least a few of them during the trip, and the only conflict was in fact caused by a couple of tall, hulking members of the blue/navy gang, who entered the carriage and decided to start trouble with me for some reason, despite our gangs being mostly on good terms. I think they disliked something about my appearance.
One of them picked me up and threw me against the side of the carriage, and I was fearing for my life. Somehow I managed to surprise him with a meat cleaver I'd acquired earlier in the dream, the only weapon I remember having, and killed them both with chops to the neck.
This, however, prompted the guards of the train to panic somewhat, and they stopped the train and ordered everyone (or at least everyone in our carriage) to disembark. We were out in unfamiliar territory, an urban wasteland. It was blue/navy territory, and at first I thought it wouldn't be so bad, and was even relieved that we hadn't ended up on the turf of a more hostile gang- then I remembered that I'd just killed two of them.
My friend in the Yellow group found our predicament most amusing. They had strength in numbers, and they weren't overly hostile with the blue gang anyway.