I'm another who prefers brass wire for spears -- or bronze actually, I think, as I use brazing rod a lot. They come in a range of hardness and stiffness, but they're always easier to work than steel, and they will never ever rust. Plus, they just look nicer... until they're painted of course.
For small scale minis (10-15mm) I use long (50-65mm) brass sequin pins, or if I can find them, entymologist's specimen pins, which are super-fine.