While Gibbs, Ziva, and McGee are in the Nelson's nursery, Tony enters soaking, glistening wet (face, clothes) from being caught in a lawn sprinkler. But if you watch the scene carefully, one second to the next, he goes from fully drenched, to somewhat wet, to fully drenched, to somewhat wet, back and forth.
The petty officer was shot by a shot gun at close range in the opening scene. There would have been extensive gun shot residue (GSR) on his clothes, that Ducky would have seen before pulling off his tear-away clothes. But obviously Ducky didn't see any GSR because he was surprised when he saw that the victim had been shot.
In the first scene when the petty officer is in the accident they show the air bag deploying several seconds afterward. This cannot happen. An airbag is fully deployed within milliseconds after impact. If it did not go off when he hit the other car it is not going to. This accident probably would not have set off the air bag anyway. There was no noticeable damage to the truck.
When Gibbs and Adrian were discussing Adrian's possible involvement with Heidi in the laundry room, Gibbs had reset a tripped circuit breaker by flipping the switch directly to the "on" position and thereby turning the lights back on. In order for the breaker to be properly reset, it would first have to be brought from the neutral (or "tripped") position to the "off" position. Only then could it be brought back to the "on" position to re-energize the circuit.
When McGee, Tony and Ziva are sitting in the Squad room and Tony is smelling a doughnut and Ziva says "Gibbs does not accept apologies, but I do" a little after Tony says that he will get back to you right after I shame McGee and gets up. After Tony says "Any one of them could have a score to settle, the problem is they all have solid alibis" You can clearly hear the name David is a low tone come across the track. This is unknown if someone off camera was talking to David McCallum or someone else named David and it was just picked up by the microphones.
When the team are entering the house, the reflection of a camera man is visible in the door window.
Worn brake pads won't cause the brakes to fail on a car, so replacing the good brake pads with the worn set would be an ineffective way to tamper with a vehicle. At worst they will ruin the rotors once the pads are worn down to the metal backing, as the displayed pad clearly wasn't.