343 Guilty Spark's single bulb is supposed to brighten whenever he speaks, as he does in Halo and Halo 3. However, in Halo 2 due to a bug the developers were unable to fix prior to launch, his bulb dims as he speaks.
In the level "Quarantine Zone," Miranda Keyes' hands are empty. When Johnson calls out for his marines, Miranda Keyes' hands surprisingly are holding two submachine guns even though we do not see her draw them out.
During the invasion of Earth, it shows several Covenant and human ships entering Earth directly over Africa to get to Africa. However, the angle is too steep that you would hit Earth directly and crash. The best way to get to Africa via space is to enter the atmosphere over South America at a safe angle.
On the level The Great Journey, Miranda Keyes holds her hands like she is holding a gun, but they are empty.
Grammar mistakes in subtitles.
If you use a Ghost to push a crate up against a wall and then shoot it, plasma burns appear on the wall behind it.
The barrel of the shotgun is too small to be of the 8 gauges that it is supposed to be according to the series canon.
Cortana is inserted into one part of High Charity and removed from another despite her chip only being present in the place that she was inserted into.
Cortana states that the detonation of In Amber Clad's reactor will destroy both High Charity and the ring, but High Charity is not close enough for this to work.
If you shoot Sergeant Johnson as the Arbiter, he says things like "Stop it, Chief".
Cortana states that there are Wraiths on the far side of a chasm, but there is only one Wraith.