All of them sounds good to me, but my least favorite are "tirarme and echarme", by the intensity of the act (a gorge is kind of a big jump) y would use lanzarme.
Now, about connotations :
from worst to the best
Tirarme has definitely the worst connotation (almost like giving up) as tirar almost means to throw away.
Arrojarme has a mid level connotation, not bad or good, but is not neutral either, as when you "arrojas" mostly is to the unknown and unexpected
example: "ser arrojado" is an expression of someone who fears nothing but also expects the worst.
Echarme is the true neutral connotation, and so neutral it actually depicts laziness as when someone "se echa" is almost like lying down.
On the other hand Lanzarme has an adventurous connotation, like going to the adventure and the unknown but like a lance, sharp, fast, brave and directed.
in contrast to "ser arrojado, "ser lanzado" is someone who goes for the victory
Remember that poetry is more about the embodiment of the feelings that the one of the actions, and if you want to tell that someone is jumping on a cliff you don't need to put it exactly into words...
we can change "echarme" or "tirarme" to "perderme"
we can change "lanzarme" to "atreverme" or "enfrentarme"