I wouldent want these wires to turn into some sorta hot knife if grounded out!
You've indicated you want 20mA for the LED, and a 12V battery.
While "unconventional", you could always put the resistor right at the battery rather than at the LED.
A 470 ohm resistor will limit LED current to about 21mA with the added advantage that even if there were a dead short somewhere along your wiring, the current will be limited to 25mA - nowhere near enough to get hot or burn.
500 ohms will limit LED current to 20mA (at your stated 12V, with 2V drop across the LED). Higher resistances will lower LED current further, and also (obviously) limit short current even more.
A circuit so arranged is pretty safe even without a fuse because you've limited the current so much. Note, the resistor will need to be half-watt or better.