Continuity mistake: When Elliot is talking with his 'buddies' in a bar his shirt collar is hanging over his brown sweater. But in the next shot as he's walking over to Alison, his collar is tucked under it. (00:07:50)
Continuity mistake: When Elliot first walks to the Devil beside the snooker table you get a wide shot and you can see all the snooker balls on the table. The position and colour of the balls change in a later shot when the Devil takes a shot and pots all the balls. (00:09:50)
Continuity mistake: Elliot is given a contract in the Devil's office. In one shot the contract is hanging off of the edge of the table. But a couple shots later, when the Devil picks up an apple and walks by the table, the contract is further onto the table, in a different position. (00:21:20)
Continuity mistake: When Elliot is in the Devil's office, the Devil goes over to a side cabinet, and picks up an apple. Next to the apples is a vase of roses. The position of the roses changes from when the Devil goes to pick up the apple, to the next shot, when she walks over to Elliot. (00:21:40)
Continuity mistake: When Elliot is on the beach with Alison, we get many shots of the beautiful sunset which continually makes him cry. But you can actually see blue sky behind Elliot as he sits and talks to Alison. (00:39:35)
Continuity mistake: When Elliot is this red-haired guy on the beach, he gets his mouth kicked full of sand. But when he stands up one second later and talks to the boys, his mouth is completely clean. (00:42:45)
Continuity mistake: When Elliot's the basketball player, when he scores the slam-dunk and breaks the headboard, he breaks the headboard after the slam as he bounces/hangs off the headboard. But in the replay he breaks the headboard as he makes the slam and then bounces/hangs off the headboard. (00:49:10)
Continuity mistake: After Elliot walks out of the elevator after becoming the charming, articulate man, the elevator doors shut twice behind him. (00:55:30)
Continuity mistake: When the Devil is a substitute teacher, the position of the big pile of apples on the her desk changes between shots. (01:01:40)
Continuity mistake: When the Devil is a teacher in the classroom she is erasing homework assignments off the board. In the close up shots (and maybe 1 or 2 of the far away ones) the board's partially erased. In most of the far away shots however, the board isn't erased. (01:01:50)
Continuity mistake: Elliot is hanging from the trifork in hell, his shirt is smoking and is close to catching on fire. The angle changes and there is no smoke then changes back and there is smoke.
Continuity mistake: At the beginning of Elliot's basketball player wish, he makes an amazing slam dunk that shatters the glass. Pay attention to the scoreboard before he makes the shot. The final score is displayed before he even score the final points.
Continuity mistake: In the basketball wish scene, Elliot is dancing and celebrating his success when he leans right up to the camera to yell something. When he leans back for a split second his eyes change to blue, his natural colour, then back to brown again.
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.
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.
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.