Looking at it with the laws of real life, Luffy should have little trouble with Enel, since Rubber doesn't conduct electricity. Wouldn't that be anticlimactic, Luffy walking up to Enel and simply beating the life out of him
I thought that Crocodile was invulnerable to physical attacks as well, but they found a way (even though I thought it was pretty lame) to make him less godlike. But on the other hand, Enel is supposed to be godlike.
Maybe he'll even pull an 'Aizen Sousuke' on them.

That's so great about OP.. you approach it with logic, and they throw it right back in your face

As for the one to be going down first, I think it will be Gan Fall...
Enel is about to kill Wiper and Gann Fall will take the blow, saving Wiper's life.