I love the way Jack shows Ennis he already has a lit cigarette right after Aguirre says "You ranch stiffs - you ain't never no good." Ennis offers him a drag of his smoke in a commiserating manner, and Jack, still pissed about the dirty punch, just turns his right hand enough without even looking at him as if to say, "Yeah, suck on it - I got my own."
By the way... this is an incredibly good observation! Awesome. I've never noticed that before.
I love the symphony of expressions on Jack's face during the reunion scene. Going from delight at first seeing Ennis/ during initial hug, to slight confusion while Ennis is pushing him to the wall, to the half-crying/ half-in-ecstacy look on his face as he clings to Ennis's face, etc.