Chewcocca

Your strength and poise through this is really something. You are so calm and self-assured. What a complete and total badass.

Still had your pants up?

Absolutely. The train has the power to swat him like a bug, but McNulty is defiant of that power. Not just defiant, but contemptuous. He doesn't think his actions are going derail the train. He doesn't have some cunning plan. There is just something in his nature that flirts with this self-destruction.

It also reveals a lot about Bunk. He cares about McNulty. He genuinely doesn't want anything bad to happen to his friend... But there is no chance in hell that Bunk is going to step in front of that train to try to save McNulty. He knows he can't fight a train, and he knows that fighting McNulty won't help.

It tells us pretty much everything we need to know about these characters, their relationship, and what to expect from them. Truly brilliant scene, imo.

He's got a fun role on Veronica Mars too, if you haven't watched it.

The Keeblers pay their debts.