I have a couple stories where I've seen some pretty interesting street weapons used:
I used to spar with a group of guys outside at a rec center in San Diego. One day there was a big circle of guys from the local high school in a big circle. They were a gang and were having new members fight each other inside the circle. We sat at a distance and watched probably five fights with lots of haymakers and double legs with horrible posture. Anyway, I noticed that a number of people at the edge of the circle had weapons. About ten guys had those small novelty basesball bats that are about a foot and a half long. One guy had a long sock with something heavy tied in a knot at the end, and one guy had a balisong. None of these weapons actually came into play. At some point some other group of guys came over and started arguing with the first group. Group 2 starts walking off, yelling that they'll be back later. At that point we decided we should leave, since we figured they might be coming back with some more sinister weapons.
Another time a bunch of angry teenagers were causing a scene on the trolley. One of them had one of those small bats and was pounding on the trolley handrails, scaring a bunch of kids and pissing off some dads. I tried to reason with them to avoid a brawl and some chaos ensued.
When cruising around Mira Mesa I happened to see a fight where a guy was hitting another guy with his belt, swinging downward strikes with the belt buckle. The unarmed guy shields his head, rushes forward and grabs the belt, and starts punching with his free hand until the first guy lets go of the belt. They back away from each other and exchange some angry words, then part ways.
One other time I was walking next to a little stream going into the bay (a little area called Rose Creek). There's always a number of homeless guys hanging out there. Across the creek I saw two homeless guys start fighting. One was sitting down and the other started hammerfisting his head with a beer can. It was pretty loud. As he's getting beaten, the guy starts standing up and I could see that he was bigger than the guy with the can. The bigger guy throws some wild punches to the other guys face, and when the guy leans forward big guy snap kicks him in the face. As big guy advances forward with a sort of guard up, smaller beer can guy picks up a rock a little bigger than a softball. He holds it up like he's going to throw it, and big guy starts covering his head by shifting between a crazy monkey and dracula style guard. Small guy sees that he can't hit the guy's head, he tries to throw the big rock at big guy's kidney area, which bounces off without much effect. Big guy finishes with another haymaker followed by soccer kicks to the ribs of the other guy. It goes to show you that pre-empting and using weapons doesn't mean you're going to win.
I used to carry a comtech stinger on my keychain, but I gave it to a girlfriend a few years ago. They're a neat little weapon that's easy to carry around:
http://www.jamesakeating.com/catalg3.htmlHere's an article detailing all sorts of brutal street weapons used in Romania:
http://www.donrearic.com/romanian.html