In one of the early flashback news sequences, the reporter warning people to stay in their homes concludes with 'CONELRAD channel' - CONELRAD was an acronym for Control of Electromagnetic Radiation developed by the FCC during the Cold War, and was abandoned in August of 1963, replaced by the Emergency Broadcast System in the same month. Any 1970s alert would have used the EBS, not CONELRAD.
The 8-track that Robert Neville puts into his car stereo at the beginning of the movie can very briefly be made out to be Frank Sinatra's "Strangers in the Night". What actually plays on the soundtrack is Max Steiner's "Theme from 'A Summer Place'".
After Neville & Lisa's night together, Lisa sits disrobed on the bed & says "Well, doctor, you certainly haven't lost your bedside manner." If you watch her face carefully, you'll see her lips never move for this line.
In the scene where Neville and Lisa are about to kiss in his apartment, the lights go out due to the generator stopping, and you hear Lisa say, "The family." If you watch closely, you see her mouth move after the words are spoken.
When the family is shooting the flaming ammo via catapult up to Robert Neville's residence there is a sound effect heard with the projected object which sounds like a flaming type noise. The last one however, while Robert is about to take aim with his gun, is thrown without being on fire, but has the sound effect to go along with it anyway.
In the lab, Robert puts a test tube in the mini centrifuge and switches it on. Centrifuges need a counter balance in the opposite slot; failing this the high-spinning rotor vibrates erratically causing breakdown.
Neville pulls out a huge spear from his chest at the end of the movie. A military doctor would know not to pull out an impalement injury without immediate medical attention on hand. As a Medical Doctor, he'd know he was dying due to the depth the spear penetrated his body. Not like there was a hospital to get taken to and be saved. So why choose to die slowly?
When Robert Neville is shooting at The Family (who are behind a car), you can clearly see a fairly straight line of bullet holes running horizontal across the car. As this happens the tires pop even though it would appear the bullets never hit near them. The scene cuts away from the car. When it cuts back to the car, the bullet holes are gone.
In the film's very first shot, Neville drives the red convertible down the street & turns right. If you watch carefully through the credits (after he fires on the Family member), you will see that he turns right again at this exact same route/street corner twice more from different camera angles, for a total of three turns. You can triangulate the shots by noting surrounding parked cars (specifically small pickup RVs) and the streets behind the car as he drives.
Neville is driving in circles or continuity error.
In the opening scenes when Neville stops to shoot at a hooded figure inside a building, his red jerry can is clearly visible before he shoots, in the back seat. After shooting he drives away, and the jerry can has disappeared. A minute later when he crashes his car, the jerry can has reappeared, but it has turned around and is lying against the back of the rear seat.
When the little girl pulls Neville's hat from the water and places it on the ledge of the fountain, the entire hat is on the ledge. When the hat is shown from the other point of view, however, it is only half-way on the ledge.
When Neville is playing chess and is firebombed, he has about an inch or so of scotch left in his glass. After he puts down the glass to use his infrared scope, he returns to pick up the same glass, which is now 3/4 full.
When Neville is playing chess with Caesar early in the film and The Family are using what appears to be a mangonel-type catapult to sling 'fireballs' at Neville's apartment, one fireball makes it just inside and sets the curtains on fire. After Neville puts it out with the fire extinguisher and turns to put the fire extinguisher back and retrieve the rifle with the nightscope, you can see the ball, now covered with the white extinguisher powder, move and see it is suspended by a string/fishing line.
In the opening sequence, right after Neville starts his 8-track, he's driving on Flower & turns left on Wilshire. The very next turn he makes is also a left - from Flower to Wilshire. This is not directionally possible - he would have to go around the block to make the same turn again. You can confirm by looking at the distinctive buildings in the background & noting where Flower curves into Hope St in the background just beyond the 4th street overpass for both shots.
In one scene, Neville and Lisa go into a drugstore and are looking at various types of medications they can use. The world has been deserted for 2 years, meaning no new products would have come in for at least that long. Medicines have manufacturer expiration dates which have been proven to be artificial. Dry pills are stable for many years past the manufacturer expiration dates. This would have been considered as a goof until only recently.
In a city supposedly laid waste, Neville has to resort to running a generator any time he requires electricity. He does so to power his apartment; he does so to power up the projector inside the cinema when he goes to watch the film. But this city with no surviving infrastructure (in the opening scenes, as he's driving around in the red convertible), all the traffic lights are powered up.
After being taken to the little room, Matthias tells The Family members to show their marks, in order to show Neville why he is not like them. You can clearly see that Zachary's white contact lens has shifted just to the right, when the camera stops on him, revealing his real eye behind it.
In the "...no phone ringing..." scene, Neville says "...it's almost dark..." and the sun is shown low in the sky, but as he drives home the sun casts a shadow from nearly overhead; just artificially dimmed.
In the beginning of the movie, when the camera pans way out to show Robert Neville walking down the street, you can see a car driving down the highway from left to right in the far left part of the screen near the tall building in the background also on the left in the horizon.
(at around 27 mins) Robert shouts out, "Matthias," and it echoes across various empty city views. However, in the last view several vehicles (including a bus) can be seen driving along a highway on the upper far left of the screen.
During the opening sequence, the camera swings down & right over a roof-top set of corpses on a sun-deck toward the street below. Right as the "Paul Koslo, etc." credit appears, a dark pick-up truck can be seen slowly rolling forward between buildings, presumably behind a film crew trying to keep the road clear for the appearance of Neville's red convertible.
In the first scene of the movie, an establishing aerial shot depicts Neville ostensibly driving through his neglected, derelict city. But in contrast to the street-level-shot footage shown seconds later of trash-strewn streets and abandoned buildings, the aerial shot shows perfectly-maintained rooftop gardens, HVAC units, clean streets, etc.
After Neville tries to chase after Lisa, but is unable to catch him, and decides to head to the bar, there is a series of four long pull-out shots of Los Angeles. On the fourth shot, it is clearly an aerial photograph taken of the city due to the sudden blurred image, and is not something that was actually filmed. Originally this claims he chases RICHIE, but it's Lisa he chases out of the store and into a park before stopping for a drink.
In the movie's opening sequence of post-apocalyptic downtown Los Angeles, when Neville drives past West 6th Street on South Flower Street, two people can be seen outside; the first near the corner by the Bank of America Tower at 555 South Flower Street, and the second in front of the Southland Hotel at 605 South Flower Street.
At the movie's end, Dutch arrives in the morning to discover Neville dying in the fountain, where he then takes the bottled "serum" that will be used as the cure for future generations, and leaves. The problem here is with the contents of the bottle. As shown in the film, the liquid is a clear red, but in reality it should be one of two things: Either it would contain drawn whole blood - which would look almost black - or it would be completely clear in appearance. The reason for this being that in order to properly separate the components, the blood would first have to be spun in a centrifuge, meaning that the bloods various elements (plasma, platelets, red blood cells, etc.) would all group together according to their weight. The end resulting product as shown in the movie, however, would have a high probability of being ineffective or even dangerous due to the fact that the "serum" is either contaminated or incompletely separated. That in itself could possibly be a death sentence to anyone attempting to use it because of the hazards of mismatched blood types - and this concoction certainly has enough red blood cells remaining to cause a severe reaction. However, since Dutch was a pre-med student (just pending the completion of his dissertation) he would know this and know how to complete the separation process to create a safe serum.
Near the end, Neville tells Lisa they will be leaving the city for good the next day, and heading for the mountains. While she is doing her final day of shopping, Neville is talking to Richie on the roof of his pad while he is filling his water tank with bottled water. If they are leaving the next day and never coming back, why would he be filling his water tank? Shouldn't he be draining his water tank instead, and taking the water with him?