Plot hole: Inmediately after Jamie Foxx finds the bomb in the city hall, and he says, "We don't tell the mayor anything", we see Gerard Butler arriving to his property next to the prison, and finally he enters his jail cell. So, in the time between Gerard Butler's arrival to the property and his entrance to the jail cell, Jamie Foxx thought about a plan, picked up the bomb, passed through the traffic and security checkpoints, talked to the warden to get access to the prison, entered solitary, handcuffed the bomb, and still had time to wait for Gerard Butler's arrival.
Plot hole: When Clyde leaves the building that he has planted the bomb to kill the Mayor and the rest of her party, he goes to his van, watches a TV feed of the meeting, then puts the van into gear and moves off. Only problem is, he didn't actually switch on the ignition, and no, Clyde didn't leave the van left switched on either, he's meticulously planned the whole operation, and isn't likely to chance his one means of escape by allowing it to be so easily stolen, and any suggestion that he'd be able to leave the van running with 'conspicuous police security' is a nonsense, as that would draw more attention to the van, something Clyde SPECIFICALLY would not want.GalahadFairlight
Plot hole: Clyde enters his cell in the final scene, and is surprised to find that he has been found out. His secret tunnel, if we go according to the characteristics accredited to his character throughout the movie, is surprisingly without any alarms of any sort. Very strange if we are to believe he is as deadly as credited. He ends dying a very silly death.