Can I use an insulator as heating element?
The goal of the heating element is to pass current through. The power dissipated as heat is V*I = I^2 * R. So you need something that DOES conduct. Besides, dependence on current, as you see, is quadratic. So if we reduce resistance by N times, we increase current by N times, you have N^2/N = N times increase in heat output. Since insulators don't conduct (infinite resistance, zero current), how are they supposed to be heating elements and get hot? I googled the nichrome as suggested by @mhaselup, and its resistance is extremely small. Other than that, it has some other important properties like withstanding high temps and oxidation.
Have a look: heating element materials