Miscellaneous: In the scene where The Gunman (Hideaki Ito) and Shizuka are intimate, you can see that The Gunman has had some kind of booster shot on his right upper arm that has left a scar. You see this as he takes off his shirt and then jumps into the bed. Don't think is a booster shot but more of a bullet shot scar.
Continuity: In the final scene, the Gunman goes from having a mustache and goatee to being clean shaven between shots.
Revealing mistakes: Right before the end-fight it starts to snow heavily for some reason, probably just for aesthetics. However, a thick blanket of snow covers everything except the chest filled with gold-nuggets. No snow seems to have fallen on the chest at all.