Continuity: After the lights go off, some goons shoot at where two characters are standing, only to find them gone when the emergency lights come on. Not a single bullet hole is visible in the Japanese paper screen they were standing before, however.
Revealing mistakes: In a long shot of rack-torture scene, everyone is clearly standing on a place-marker.
Continuity: While Frank Castle is fighting a Japanese Swordsman, a holstered gun on Castle's back disappears. Moments later, it re-appears in the holster. The weapon wasn't touched by anybody.
Revealing mistakes: After the Japanese henchman are shot at through the paper screen, the very last extra to be shot dies unconvincingly. He slowly drops to his knees, leans forward, and carefully places his weapon down.