When the boys are testing their powers throwing the baseballs at each other, Steve throws one at Matt and it hits him in the face, right under the right eye. Next when Matt is throwing the ball at Steve, you see the bruise from the ball on his face, but it's by his left eye now.
At the beginning of the movie as the boys travel to school in the car: the fine mist on the driver's widow becomes large drops; the sun on the trees becomes overcast without shadows; and the position of the driver's door mirror changes positions as they arrive at the car park.
During the fight between Andrew and his bullies (while he is wearing the firefighting suit) he throws one man to the furthest point of the street. He then jumps up into the air, and the camera follows. When Andrew hits the ground again, the man has disappeared.
Fifth Avenue, which travels southbound from the Space Needle, has the monorail above it, at the time, Seattle's only elevated train, which is not shown as Matt and his girlfriend are inside the car being manipulated by Andrew.
Fifth Avenue does not have a direct line to the Space Needle as shown in the movie; Fifth Avenue heading north as shown by Matt and his Girlfriend inside the car being manipulated by Andrew would be to the West of the Space Needle. There is no street or Avenue that lines up directly with the Space Needle.
In the parking lot scene when the car is moved by telekinesis, the rest of the cars in the parking lot clearly have the steering wheel on the right side of the vehicle. The film was shot in South Africa, where this is common place. It takes place, however, in the United States (Seattle), where the steering wheel should be on the left side.
The goof items below may give away important plot points.
When Matt impales Andrew at the end, we see it a second time from a second view. When we see Matt the first time Andrew gets impaled, he is holding himself with one hand. The second shot of Andrew getting impaled shows Matt when he impales Andrew lands on his side. Then when we see Andrew again, he is back to holding himself up.
When Matt and Andrew are battling it out in the Seattle night scene, as a helicopter flies overhead the radio calls out from an officer that he is "Eastbound on Yesler," which, when heading eastbound on Yesler Avenue it takes you away from downtown and away from the Space Needle - in other words, away from where the action was occurring.