Plot hole: Rhona Mitra is told she can't fly into Scotland because it's a "no fly zone." But it's all part of the UK, and she's being sent in as part of a UK government operation. The only group enforcing the no fly zone would be the UK government, so they could send her in via whatever means they like.
Plot hole: When Ann and Runaway are fleeing from the dinosaurs in the car, suddenly a fence flaps into the screen and blocks the ways of the running dinosaur. This makes no sense and is never explained, since none of Ann's friends or anybody else is anywhere around there to manage this, nor is the fence ever mentioned, nor is there any other (reasonable) reason that the fence would block the way exactly in this moment.
Plot hole: Batman finds at Belson's home a handwritten list of substances needed for a transplant. Why would Belson, a medical authority in the field that knows those things thoroughly, even write a list down? If it's for Freeze to procure him the material, why would it be at his house and not with him, and when did he even have time to be at home to do that, since he has been kidnapped by Freeze when he was driving on the outskirts of Gotham and taken to the oil rig? If he had time to go home, he at least would have changed clothes, he's still in the tuxedo he wore when he was kidnapped the night before.
Plot hole: The aliens provide coordinates for a place to make a rendezvous with humans but do not specify a time. It's possible they're monitoring and will arrive when they see enough humans gathering at Devil's Tower, but the humans seem to expect the aliens to come more or less exactly when they actually do, somehow.
Plot hole: The same zombie who can smell through a vault that Gerry is not worth a bite, just minutes before couldn't smell the presence of three alive humans two meters apart.
Plot hole: After being hit with the spores, Cobra Commander cannot walk or even move very well with any speed at all. The Cobra minions have to drag him to their prison with the Joes and just leave him there on the ground after the Joes make a break for it. The Joes go quite a distance to engage Cobra. Road Block is delayed only a couple seconds behind the other Joes when he is grabbed, but knocks out the minion who grabbed him. Suddenly, Cobra Commander is at his feet telling him to wait because it's a trap. Later, Road Block has to carry Cobra Commander because he still can't move much. There's no way Cobra Commander could have caught up with Road Block to warn him of the trap. (00:52:50)
Plot hole: How did Carolyn Fry get out of the cave in the canyon to confront Riddick at the Skiff? Riddick strained to roll the rock into the cave entrance, and he was a big, strong man from a position of good leverage. How did Carolyn and the other two push the rock out of the way so that Carolyn could get out? And, then, how did Carolyn mange to push the rock back into place? It was still there when she and Riddick came back from the Skiff to bring back the other two.
Plot hole: Nick Fury wants to detain Tony as he is the only witness. Tony takes off and Nick Fury even says to apprehend him so their only witness isn't killed. Yet when the S.H.I.E.L.D. robots confront Tony at Pepper's vacation spot, they say they are authorized to use deadly force against Tony. And Nick Fury even orders them to fire when Tony resists. If they need Tony to keep their only witness alive, why try to kill him when he doesn't cooperate? (00:31:05)
Plot hole: Once Time Trapper has been stopped by Dawnstar and the time vortex in the sky stops sucking things up, everything in the air just hovers unmoving completely. Except for the people. Somehow Batman and Robin and Superman are able to move around just fine in the same time and gravity frozen place, Robin even jumps from hovering rock to rock without them moving. In fact, as soon as the sucking stops, the tree that Karate Kid is hanging onto stops moving and does not fall, but gravity somehow instantly affects Karate Kid and he almost falls off the tree and has to catch on again. It makes no sense at all for the objects to be affected and stand still and the heroes to not be.
Plot hole: Gerry's wife uses a rocket boot to break through a window and then slides down a curved wall to get to their son. She does so gracefully and takes off running. Gerry slides and takes a hard tumble and rolls down, landing on the ground. The next shot shows Gerry running behind his wife and not too far away as they reach their son. Even if it was to show a little time passing, there was not enough distance between where they broke the window and their son for Gerry to have picked himself up and catch up to his wife before reaching their son, especially with his wife being a worried mom doing a full on sprint to her kid.
Plot hole: Nell the ship made a statement early on in the movie that the Nuclear bombs that Sador was firing at her could not be destroyed, the only defense was to outrun them. Soon after Cayman dies, Sador fires Nuclear bombs at Shad and Nell, and Shad is able to destroy them by firing on them.
Plot hole: There is no way Anna could know that Hester was going to be at the auction. The circumstances that led to Hester and Tom being captured can't possibly have spread to the Anti-Traction League, they were immediately taken to the slave auction after being captured. Anna also instantly recognizes Hester when she sees her despite the fact that Hester was 8 years old the last time she would have seen her.
Plot hole: Although the errand bird always insists on the postage and even asks for additional fees for more than twenty words, he never gets any payment from the assigning characters.
Plot hole: When we first see the reanimated Sparky, his head's sewed on. While that makes him look a bit like the traditional Frankenstein monster, it doesn't make a lot of sense - the original monster had stitches on its neck because it was made from multiple body parts, but it's not like they sawed the dog's head off after it died...
Plot hole: A Bug meteor knocks out the Roger Young's communications. She dodged it at sublight maneuvering speeds, indicating that it is moving fairly slowly. If it is so important that she warn Earth it's coming (which is how we know their comm was damaged), why doesn't she jump back to tell them or destroy it herself? Even if she has no capital ship weapons (she is a troop carrier), there is no indication that her faster jump drive is damaged or needs longer than they have to warn Earth to charge for a jump, or that she can't leave her patrol station, etc.
Plot hole: Wouldn't Taylor have suspected he was still on Earth, seeing as all the apes were speaking English?
Plot hole: At the bar shootout where everyone except Marlboro and Harley are murdered, the two jump through the window, over the fence, into the airport, and into an airplane luggage compartment. They would have been caught by security. The missing, and dead, airport worker would have been missed and searched for, the gunfire would have attracted attention, and the police would have been called. They never would have left the airport.