Be Careful What You Witch For - S2-E22
Plot hole: When teenage Prue has run away with the demon, and Phoebe and Piper find her in the park, teenage Prue is 'killed'. Her sisters drive her home to get Leo to heal her, but shouldn't they have just been able to call to Leo to orb to them when Prue was first hurt, and heal her in the park, and save driving back to the Manor, risking Prue dying?
Suggested correction: I see orbing to the park but he didn't heal her, she was already dead and he can't heal the dead, that's why the genie brought her back - that's what Phoebe wished for.
But if they would have called for him right away - he would have been able to heal her before she died. However at this point in time I don't think they knew how to call for him.
100 Light Years From Home - S5-E19
Plot hole: At the end of the episode, Dawson is seated in the kitchen talking to Pacey in a normally loud voice. At the same time, Joey and Charlie are awake and talking in the pup tent in the living room, very close to the kitchen. Later in the Season we learn that Joey had no idea Dawson had driven down to Florida to see her, as apparently he left without seeing or talking to her. But being in such close proximity that morning; there is no way Joey would not have been able to hear Dawson's voice as he talked with Pacey. The living room was close enough to the kitchen, so it doesn't make sense that Joey wouldn't have known Dawson was there and if she did-she would have gone to talk to him.
Plot hole: During the episode "Superstition", Onizuka thinks he has cancer because the magnetic pain-pads he was wearing created strange blobs in the X-Ray he has taken. However, given the fact that the X-Ray was so strange, doctors would have given him a complete physical, and noticed the pads much sooner. Here, they literally just assume he has tumors, and fail to ever take notice of the pads. Simply impossible, given the gravity of the situation. (Obviously, this is to pay off at the very end of the episode.)