It really depends. Glass, for example, does a fair job at conducting heat, but it is an insulator to electricity, which is why it is usually used for the insulators on power lines. Metal, on the...
Good conductors are not good insulators because a conductor (such as metal) attracts heat and lets it pass through itself, while an insulator (such as glass) blocks or traps heat and does not let it...
I'm assuming electrical conductor - Several spring to mind. Carbon is pretty bad at conducting electricity but it will do it, which is why electrical resistors are made of them. Semiconductors such...