When James and Carl (Estevez & Sheen) are running after the flat bed truck with the hazardous drums, James is seen carrying the BB gun. When both characters jump on the back of the truck the BB gun is gone. The next image the BB gun is slung over James' shoulder.
When we see at night, Carl and James' rival truck drivers waiting in their car at night for the chase, the back window can be seen to be clearly smashed with a hole in the middle. Later on, the same window is not smashed.
In his office, Maxwell has an odd looking map showing current daytime in the world in the form of a light source. According to that map, it's daytime in California but when it cuts back and forth to the hitmen he is talking with on the phone, it clearly is nighttime.
The "interactive" map could of course be broken or just in need of a battery change which would explain the discrepancy.
In one of the camera angles where we see Carl and James throwing trash into the truck accompanied with Louis (around the time of when they find the dead body in the trash can), the shadows of the camera and cameraman's head can be clearly seen at the bottom of the screen.
When the pranksters blow up the car on the beach, the cable used to initiate the explosion can clearly be seen leading from the car on the right side of the picture, while still attached to the vehicle as it flies up into the air. It had been buried in the sand but didn't detach when the explosive went off.
In the final scene, the bad guys are off-loading 55-gallon drums of toxic waste from trucks and rolling them down a hill into a lake. However, once the drums land in the water they float, which indicates that the drums are empty.