"Studies show jogging adds years to your life. But then you spend them jogging."
How did I miss this thread before now? Now there's so much to catch up on! My first reaction was, none of the above, I'd give up something really tiny, like the scene of Ennis throwing hay off the truck -- and immediately realized, no way, I want every single second of Ennis intact. How about Jack showing Bobby how to drive the combine -- no, that scene establishes Jack's nice relationship with Bobby (in contrast to Jack's with his own dad).
Then I thought of the pissant scene -- perfect. It's short, inessential to the plot, virtually pointless, and seems unfair to both Jack and Lureen. Why is it necessary to establish Jack's unpopularity with anyone except for LD Newsome and maybe Jimbo? As Mikaela says, why would anyone not like Jack? And why show Lureen treating Jack disrespectfully? To me, she seems a perfectly loving wife, setting aside her increasing bitterness over you-know-what.
But Katie, I suspect you chose more important scenes to make the decision more challenging. So among those, I'd pick the fireworks scene. It accomplishes some fairly important things -- demonstrates Ennis' hot temper, gives us the memorable biker characters, shows how Ennis fights with men he's not in love with, contrasts with his less effective fighting on Thanksgiving, expresses his frustration over missing Jack or his resentment of rude heterosexual men or whatever, and sets up the iconic American image -- so striking as the finale to the movie trailer! -- of cowboy with fireworks. (I know some argue that it causes Alma to fear Ennis' violence, which to me seems unrealistic.)
But if it were omitted from the movie, I don't think we'd miss much, whereas with all the other scenes listed, we would.
Scott, now that you mention it, that DOES remind me of Billy Jack! Because Ennis kicks the one biker in the face, just like Billy Jack does when he beats up the racists! I think this registered subconsciously, but it took your post to make me realize it.