All Hell Breaks Loose: Part 1 - S2-E21
Continuity mistake: Before the Roadhouse fire, Ash and Dean are talking on the phone. Ash looks at his watch, on his left hand, it says 8:10, and has a black dial/face. As Dean and Bobby go through the rubble, Dean identifies Ash by his watch. Still on his left hand, it is now upside down, evident by the crown of the watch (used to move the hands of the watch) which previously facing his hand, is now facing his elbow. Also, the dial/face of the watch is now silver instead of black. This is a different watch, and was inadvertently put on the burnt arm upside down.
Born Under a Bad Sign - S2-E14
Revealing mistake: When Dean turns over the deceased man lying on the floor, the man blinks while Sam and Dean are arguing about whether or not Sam is responsible for his death. (00:10:25)
Factual error: When Sam and Dean are showing Jo pictures of H. H. Holmes' victims, the last picture was a victim that was not his. The final black and white is Jack the Ripper's third victim, Elisabeth "Long Liz" Stride.
Visible crew/equipment: In the scene before Dean makes the promise to Sam, as the camera pans along the side of the Impala, in the rear of the car, you can see the dolly track that the camera runs along.
All Hell Breaks Loose: Part 1 - S2-E21
Continuity mistake: In the scene where Dean is with Bobby at the burned down Roadhouse and Dean gets Andy's vision about where Sam is, the first time Dean scrunches his face in pain he puts his left hand to his head. The shot changes to a back view and you can tell his left hand is still at his head. But when the shot switches again Dean is bringing his right hand down from his head.
All Hell Breaks Loose: Part 2 - S2-E22
Revealing mistake: Sam is breathing noticeably at the beginning of the show on the bed even though he is supposed to be dead.
Playthings - S2-E11
Continuity mistake: In one scene Sam is hung over the toilet from drinking too much with his cast on his left arm. The rest of the show the cast is on his right arm. (00:20:19)
All Hell Breaks Loose: Part 2 - S2-E22
Continuity mistake: When Dean kisses the Crossroads Demon, his head is tilted left, but when it cuts to the next shot his head is tilted to the right. It switches back and forth in the next two shots too quickly for Dean or the demon to move their heads.
Continuity mistake: At The End of this episode Dean suggests they go to the Grand Canyon because they have never been, later in the series they talk about John taking them when they were little.
Other mistake: In the final scene the ECG reads in the bottom right corner of the monitor 09:06:12 19 JUL 06. When the Dr. Calls time of death he states 10:41am.
Factual error: When the doctor says that the dead man has a high lymphocyte percentage indicating a viral infection after she looks down the microscope: 1) What they show in the microscope looks nothing like what is actually visible down a light microscope (especially the supposed lymphocytes) and 2) Even if she could see what they showed, it wouldn't actually indicate that the infection was viral.
All Hell Breaks Loose: Part 1 - S2-E21
Factual error: Dean finds a body in the house that burned down. The arm has a metal watch still on the wrist with hardly any damage. It has some black soot on it but that's it.
Suggested correction: Your entry is based on opinion/theory only. It's possible for someone who died in a fire to have parts of their body to not be affected by the fire.
What Is and What Should Never Be - S2-E20
Audio problem: Dean is in the cemetery talking to his father's grave, trying to figure out what's happening to him. In a continuous shot, right after Dean says "like it doesn't want me to be happy", you hear him say, "of course I know what you'd say" but his mouth doesn't move at all. (00:23:00)
All Hell Breaks Loose: Part 1 - S2-E21
Visible crew/equipment: When dean and Bobby drive to the burnt down road house, you can see the boards holding up the wall in the set at the old front door, the boards are set at a right angle to hold the wall up but definitely wouldn't be there it the place was intact.
Tall Tales - S2-E15
Other mistake: When Dean is telling the Trickster that he likes his style it shows the same shot of Dean twice saying "I do, I mean..."
Other mistake: When Dean is having fun with the Magic Fingers and listening to music, the song displayed says Led Zepplin - Kashmir. Further listening proves it to not be Zepplin at all. (00:05:45 - 00:06:30)
Other mistake: Dean is tied to a chair when Sam rescues him. His hands are tied to the arms of the chair with rope. Sam comes over and just casually loosens the rope and it comes right off, then Dean just simply flings the rope off the other hand like they weren't even tied up, Yet before Sam got there, Dean was struggling to get loose.
Children Shouldn't Play with Dead Things - S2-E4
Revealing mistake: When Dean is talking to the girl about Angie, she's crying hysterically and using tissues yet there's no tears coming from her eyes.
Simon Said - S2-E5
Factual error: The man gets hit hard enough by the bus to knock his shoe clear off, yet when we see his body about to be covered up, there's only a small amount of blood on his mouth. If you get hit by a bus hard enough to make your shoe fly off, then there should have been more damage.