If you are into flint knapping but are low on supplies of good rock, I suggest trying broken glass from bottles. It can be knapped into very satisfactory arrowhead or knife point. Plenty around as well.

Old tv glass works too, or so i have heard.

Yeah, I got a cut on my finger from a spalled piece of obsidian the other day, and it didn't stop bleeding for several hours, even with a bandage and constant pressure. Of course, it didn't help that I accidentally pulled the incipient scab off the cut with the sticky part of the bandage, but that little bast**d was surprisingly sharp, even to me! Remember kids, don't be like Bleedin' Ole Jack, and wear Gloves! Can't stress this enough, SAFETY FIRST.