Well, It is NOT his blaster, which is in his holster the entire scene, and the scene following it. And it doesn't have any cloth parts. Plus. why would they have him dangling there with the thing in his holster the whole time, knowing he's supposed to look down at it? It's probably just random debris, to show scale, like someone said.
I also always thought it was his hand, because of the cylindrical portion, and the cloth piece (sleeve?) that seems to blow in the wind. But I got slammed for starting this exact thread about 6 years ago. I thought Luke seeing his hand falling away was supposed to give a sense of loss...closure....his failure. Like when he looks down at his hand in Jedi. Whatever.
But that cartoonish and contrived comic book EU keeps coming up as an explanation, so..... it MUST be right.:lol Hey whatever happened to "Jaster Mereel"?:lol (Awesome name, btw). I always feel sorry for all the kids, growing up not knowing that other people have decided that they haven't seen the whole story.:rolleyes Poor things......their stupid parents only showed them ALL SIX movies..........