I'm making a heavy metal cake this week complete with skulls and other crzy things. I'm thinking that the best border would be something barbed wire looking.

Any ideas on tips to use? I know that I could free form it, but I wanted to see if anyone had a better idea?

If you use a big round tip, like a 12 you can make really good looking spikes! Just begin like you are making a round bead but pull up while squeezing...it looks great in black with some silver luster!!

I like the spike idea.