When the real estate agent informs Hal about the deaths in the town, a man is shown with his face melted by steam. As the steam continues to spray, the man gradually fades from one position to another.
When the twins first find the monkey, one turns the key on its back, thinks it's broken and tosses it to the other twin. The monkey is thrown facing backwards but is caught facing forward.
If someone dives into electrified water, they get electrocuted. They don't explode.
The movie starts in 1999 according to a caption. Then the movie skips 25 years into the future according to another caption, but later the movie states it is only 2016 which is 17 years after 1999.
The harpoon gun that the scuba diver statue had in the opening scene should not have been real, since its just a decorative item. If it were for some reason real, the pawn shop owner certainly wouldn't have kept it cocked and loaded, pointed in the direction of his counter, specifically to prevent what happened.
Hal and Bill's room has a Nintendo Gamecube controller sitting near the TV. The Gamecube did not release in North America until November 14th 2001 and the scene is supposed to take place in 1999.
The girl who jumped into the pool should have heard the air conditioner fall and crash on the ground before she jumped in. Yet she didn't even seem to be aware of it.