Mike is walking around most of the movie is a blue tank top, sweat pants, revealing white socks and dark sneakers. There's no where for him to hide or place a gun or anything else but he always takes a gun out whenever he needs one.
When Mike goes back to the Helicopter Rental garage to confront the manager, the secretary tries to stop him. She explains that someone just showed up using his name and badge number. Mike realizes that David stole his wallet and badge. He feels around for his missing badge even though he's wearing sweat pants with no pockets.
When David calls a "bookstore" in Los Angeles to research what kind of helicopter was involved with Susie's kidnapping, the woman in the bookstore answers the phone without giving the name of the store. She just says "bookstore". She answers on the first ring but David reacts as though they haven't been answering their phones all day and the first thing he says is "you guys don't answer your calls anymore?" This is the only time we see him calling.
The female voice of the Police Dispatcher is the exact same voice as the girl who drops off David at the McDonalds. And even though it's all supposed to be in Los Angeles, it was mostly shot in the Philippines and she has a Filipino accent.
When David's female student undresses and gets in the jacuzzi naked, David joins her but he is fully dressed in one shot and two seconds later he is completely nude walking passed the camera but no time is supposed to have passed.
When we first see Mike, he chases a "suspect" over a fence and ends up on the other side of an alley. There are two guys waiting, ready to fight and attack as though they were expecting him. But there would be no way for them to know that he was going to end up there. Then when the fight is over and Mike defeats all three... he takes one to question him but it's not the one he was chasing in the first place and we never get to see what he was questioning him about.
When David hands the owner of the Helicopter Business 500 dollars for information, the bills are disorganized as he messily folds them together to hand to the man. But in the very next shot the bills are organized and folded neatly.
In the scene where David and Mike confront each other in Lillian's house when they are pretending to be gardeners, David is downstairs talking to Lillian. Mike walks down the stairs to find them talking. He appears to be on the left when he sees them but he approaches from the right.
In the climactic cabin scene, Susie lays unconscious, on an explosive rigged cot. If any weight is put on it or removed from it, the cot and cabin will explode. David and Mike replace her with jugs of water that they figure weighs as much as she does. It works, but not long after that, the cabin is sprayed with bullets. The jugs of water are shot full of holes and the water pours out. The lost water should have detonated the cot but it does not.
During the opening credits, they splice together random shots around Los Angeles, including seedy neighborhoods to set the tone for the story. In one of the shots you can see someone attempting to break into a locked parking lot with a large piece of wood and another guy (presumably homeless) is close to him with a shopping cart filled with garbage. They turn and look towards the camera obviously shooting them from a passing car or van. They see themselves being filmed. One picks up a piece of wood and threatens the cameramen who turn off the camera and you can see the screen go white just before the cut to another shot.
Lillian tells both David and Mike that they are specifically the father of Susie so she can use them to help get her daughter back. Even though the question of who the father is, is a point of contention between the two men, they never once ask Lillian which one of them it actually is.
In the "merc" bar fight, when David kicks a number of mercenaries, it's clear that he doesn't even come close to touching them, appearing to be at least half a foot away, yet they fall and react as though he did connect with them.