How would you make your own resistor of any arbitrary value? What natural material works well? I've made my own inductors out of tin foil, then capacitors out of mineral oil, and would like to move on to resistors. Any advice would be grateful.

I should note that the resistor should be durable and reliable.

Find some Nichrome wire. Measure its resistance for a given length. Then cut a length equal to the resistance value needed and wrap it around a dowel or cardboard tube. Dip the whole thing in epoxy. There's your resistor.

Those wires tend to be 20ohms per feet, which is useful, but not universal. I use a lot of 10K resistors. In that case, what should I use?

anyone knows where i can get conductive plastic?

http://www.sci-journal.org/reports/vol3no1/v3n1k44.html