Plot hole: At the beginning of the episode, Eric and Jack call the cops on Luther for planning an illegal rave at the college, but the cops let him go because he had not started the rave. He still broke into the student union building, and therefore should have still been arrested. He even threatens Eric and Jack afterwards right in front of the cops, and they do nothing about it. (00:00:20 - 00:02:10)
A Midwinter Night's Dream - S1-E17
Plot hole: Niles makes up Frasier's couch to sleep in and when he lies down he lets out a yelp - and pulls a plastic pirate's hook from behind the cushions. Earlier Niles had appeared wearing a pirate's costume but at no point did he have a hook, nor did he go near the couch. His overcoat had been on the floor the whole time so it couldn't have come from there. It would have been difficult for it to get behind the cushions unless deliberately shoved there, which we never saw and makes no sense anyway.
Plot hole: Earlier in the season, it was established that The Jem'Hadar are genetically engineered to be loyal to the Changelings, meaning they will not deliberately harm them. With that in mind, the Changelings still care about Odo's well being despite his refusal to return to them. So why didn't the Lovok Changeling send a message to The Jem'Hadar ships to inform them that a Changeling was going to be on the runabout? Given that he took time to offer another chance to return to his people, you would think he'd take time to make sure he returned to the station safely.
Suggested correction: Maybe The Jem'Hadar were trying to disable the runabout to try and capture Odo and Garak.
Plot hole: "Showdown": Darien's lost hat and jacket reappear without explanation after Kane finds him wandering in the desert. Also unexplained is how Kane conveniently happens to be leading an extra, unnecessary horse - unnecessary, at least, until he stumbles across the stranded Darien. (00:15:00)
Plot hole: In the ending scene, Mike has a probable concussion from her fall, so Sully keeps her awake to prevent her slipping into a coma. They talk all night, reminiscing as Mike experiences periodic pain spasms. Their talk ends with discussion over them having another child, and then they instantly engage in an intimate moment, which would be impossible, considering her condition, and without further checkup from another doctor. Sometime later she is suddenly feeling 'cured', and they return home.