This method produces the most attractive, cheapest barbed wire possible but is not the fastest way. Still, we all have to suffer for our art :)
This barbed wire is attractive because it is made from real wire, and this lets it fold, drape and stretch like real wire.
As I say, this is a little time consuming... it will take an hour or so per meter of length but I urge you to try and make a short length... maybe 10cm... just to feel it and see how cool it is.
As an added bonus, the little barbs are capable of drawing blood just like the real thing.
Making it is really simple too. All you need is wire and a craft knife.
Start with some normal wire from the hardware store. Strip out the thin strands of copper wire from inside.
Grab three of these strands and tie a basic knot in them.
Pull the knot tight.
Carry in doing this. How close you get the knots really depends on your patience. Aim for no more than 1cm between them to get the best effect.
Once you have got a length you want, tease out one of the strands from the three and cut it close to the knot. The little pieces left over will form the barbs.