Kids' creativity, as measured by the most recent Torrance Tests of Creative Thinking scores, has been sliding since 1990, most noticeably among our younger students. Reduced music and arts education is cited as a key factor.
I like to use the 'demolition grade' blades. They ll cut wood, metal, plaster, wire, or pretty much anything you d care to throw at them. They're made from decent carbon steel that will take and hold an edge rather well. When bought in packs of a dozen, they can be had for about a buck each.
Obsidian can be used to make extremely sharp knives, and obsidian blades are a type of glass knife made using naturally occurring obsidian instead of manufactured glass. Obsidian is used by some surgeons for scalpel blades, although this is not approved by the US Food and Drug Administration (FDA) for use on humans.