Continuity mistake: When the demon manages to break through the mirror it's stuck in, its hand comes through the mirror. When it cuts its hand is nowhere in sight. (00:08:10)
Continuity mistake: When Constantine manages to get the mirror through the window he falls on his back. To the right on the screen a chair lies on the floor beside a dresser. A few shots later when it cuts to Constantine getting up we can see the chair has changed position as its back now covers the opening of the dresser. (00:08:15)
Continuity mistake: When they are luring the demon into the mirror they have tied a chord to it. When the mirror come flying out the window we can still see the chord tied to it. But when it cuts to the mirror falling down hitting the car the chord is gone. And don't tell me the chord just went off, because it was tied quite well. (00:08:15)
Continuity mistake: When Constantine and Chas gets in to the car and Chas is angry about Constantine dropping a mirror on his car, Chas has his hands down. When it cuts his left hand rests on the steering wheel. (00:10:20)
Continuity mistake: When Angela walks out of the confession box she grabs her necklace cross and holds it. When it cuts from behind her, both her hands are down. (00:11:15)
Continuity mistake: When Constantine is looking at the X-rays of his lungs he says "And now I'm gonna be done in by this." and lowers his hand. When it cuts he does the same. (00:14:10)
Continuity mistake: When Constantine is seeing the doctor about his cancer you can see the lights on the screen showing the X-rays are on. When it cuts after she says "This is aggressive", the lights are suddenly off. (00:14:15)
Continuity mistake: In the X-ray room when Constantine has lowered his cigarette he is standing next to Les and walks away. Their conversation goes on for a couple of shots and then suddenly he is standing right next to Les again and walks away. (00:14:15)
Continuity mistake: When Constantine gets the cigarette box he slides it across the table. Later there is a close-up of the cigarette box and we can see it has moved closer to the edge of the table. (00:17:50 - 00:19:00)
Continuity mistake: When Constantine is having his chat with Gabriel, after he asks what 'He' wants from him, and Gabriel says "Only the usual. Self-sacrifice. Belief.", it cuts and we see Gabriel resting her hands on her lap. When it cuts her left hand is on her knee. (00:21:55)
Continuity mistake: When Constantine has a sip from his cough medicine, we see the Vermin Man approaching him in the background. A few shots later we see the Vermin Man is still approaching him but he is still moving in the same spot as earlier. (00:26:25)
Continuity mistake: When Constantine and Chas are heading for Midnite's the first time and Constantine says "You're reading too much, kid. It's a bar", you see Constantine walking with his hands down. When it cuts, he's holding his cigarette to his mouth. (00:28:05)
Continuity mistake: When Constantine and Chas comes to Midnite's bar and the bouncer holds up the card, we see him holding the card between his thumb, index finger and middle finger. When it cuts, he holds it between his thumb and index finger only. (00:28:30)
Continuity mistake: When Constantine is heading for Midnite's office, he stops by his door. A man opens the door and walks out passing Constantine. At that time you can see the background is full of people. When it cuts to Constantine walking in the door the background has changed, the people are gone and a blue wall has appeared instead. (00:29:35)
Continuity mistake: Constantine catches a spider under a glass and blows some smoke in it. The amount of smoke in the glass differs between shots. (00:33:25)
Continuity mistake: When Angela visits Constantine you can see an ash tray and two bottles along with other stuff on Constantine's table. Later, when the demons fly outside Constantine's window, as the camera moves over the table you can see all items has suddenly been removed from the table. (00:34:40 - 00:36:10)
Continuity mistake: When Constantine tells Angela to leave the room you can see the cat sits on his lap with its back against the camera. When it cuts the cat is now facing forward. (00:40:55)
Continuity mistake: When Constantine gives Angela Isabel's name tag, Angela is holding the tag so that half the tag is between her fingers and the rest of the half inside her hand. When it cuts half the tag is still between her fingers but the rest of the half is now outside her fist. (00:44:30)
Continuity mistake: When Father Hennessy stabs himself with the cork opener the items around him change position between the shots. (00:47:55)
Continuity mistake: When Constantine submerges Angela in to the tub he pulls up his right arm from her head. When it cuts to a shot under water he pulls up his arm again. (01:04:00)
Chosen answer: According to the legend of "The Spear", it is indestructible.
Nick Bylsma