Funambulist

fun-am-bu-list (fy-nmby-lst)

noun
1. A tightrope* walker or practitioner of funambulism.**
After being told all his life that he was walking a fine line, Garfield became a funabulist.

Synonyms: tightrope walker.

* It's not really fair to specify, since it can mean slack rope too, but that's just not as fun!
**Funambulism is the art of rope walking.