Continuity mistake: At the very start of the film when Elliot is holding the door open for the people and they start to rush in at a very high speed, if you look closely about halfway through you will see the same people going in like in the first half of it (Especially look for a woman in a light blue suit). The clip is just being replayed.
Revealing mistake: In the scene when Elliot speaks Spanish, there's a mix of different Latin American accents, and what he is saying does not make much sense to a Spanish speaker.
Continuity mistake: When Elliot refuses to make his last wish, the Devil extends her hand fully forward to send him to hell. In the next shot from behind her, her hand is raised.
Continuity mistake: When Elliot wakes up as the Colombian drug dealer he looks over at Allison then at the wedding band on his hand. Then when he walks over to the mirror the wedding band is gone.
Continuity mistake: When Elliot and The Devil (Liz Hurley) are in Alison's bedroom, Liz tells Elliot that Alison is in the shower. Elliot goes to take a look, but notice the bed in the middle of the room. We see a shot of him and the bed, a shot of Liz then a shot of Elliot walking to the bathroom. So, in reality, Elliot walked through the bed to get to the bathroom, but it is back in the next shot.
Continuity mistake: Brendan Fraser's tie seems to magically disappear every time he is warped back into the present time. Watch from the beginning to about the middle of the movie, his tie is gone and his shirt bottom opens.
Continuity mistake: When Elliot is the Colombian drug dealer and is having an argument with his wife, she throws a glass of some liquid at him but it hits the door and the liquid splashes across the door. She then throws something else at him which also hits the door, but the door is now completely dry.
Continuity mistake: In Elliot's basketball player wish after the game you can see the sweat/water dripping on his face only when the camera is on him. When the camera focuses off him it stops only to magically appear when he starts speaking.
Continuity mistake: The Devil gives Elliot a pager and she tells him that if he wants to get out of his wish he should dial "666". In some wishes he presses the "6" three times and is transported out, in others he presses the "6" three times and then presses another button and is transported out and in the sensitive guy wish he presses the "6" four times.
Answer: It definitely is a Montegrappa Oriental Zodiac pen, this brand has been making pens in Italy since 1912. I am not sure which of the three red pens in that collection (Oriental Zodiac) is the one seen in the movie, but given its association with the devil, my guess will be it is the Ox fountain pen.