These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Waingro is an Ax-CrazyPsycho for Hire hired by criminal Neil McCauley to help in the robbery of an armored truck. When one of the guards "looks at him funny," Waingro murders him, necessitating the deaths of the other two guards to eliminate witnesses, turning a bloodless robbery into a triple homicide. His accomplices, disgusted at Waingro's actions, try to kill him in retribution but Waingro manages to escape. To get revenge on his accomplices for the attempted murder, Waingro approaches money launderer Roger Van Zant, whose buyer bonds the group stole from the truck, and offers to work for him. Waingro tracks down McCauley crew member, Trejo, holds Trejo's wife hostage, forces Trejo to sellout information on his crew's bank heist, and then leaks that information to the cops. This leads to the shootout with the cops which claims several lives. Waingro then murders Trejo's wife and beats Trejo half to death, but refuses to kill Trejo himself because it's more painful for Trejo to leave him live. Instead, McCauley kills Trejo at the latter's request.. Waingro is also a Serial Killer of underage prostitutes, whom he solicits then kills by bashing their skulls in. Neil and his crew may be criminals and killers, but they still have honor and standards. Waingro is just a psychopathic maniac.
Crowning Music of Awesome: The final shots of the movie before the credits where Hanna holds McCauley's hand as he dies are set to Moby's "God Moves Over The Face of the Waters". And it is glorious.
Harsher in Hindsight: The film is known for the climatic bank robbery scene, where Neil and his gang get into a gunfight with the police and shoot up Downtown LA with automatic rifles. Except that two years after the movie came out, a pair of real bank robbers held up a bank in North Hollywood, then were killed after a 44 minute shootout with the LAPD officers. No police officers were killed in the North Hollywood shootout, but some were badly wounded, and this shootout lasted 44 minutes, whereas the film's shootout lasts under seven minutes.
The robbers of the North Hollywood Shootout reportedly watched this film numerous times.
Moral Event Horizon: The audience already knows that Waingro is an unstable and violent character after he shoots the first guard during the armored car robbery at point-blank range for no good reason, but the scene where he kills the prostitute, then the scene where Hanna visits the crime scene of another one of Waingro's victims, exists solely to push him into this in order to demonstrate how Neil and his friends, while still violent criminals, are much better people than him, even though Neil and his crew members use assault rifles during the bank robbery shootout and bring down several cops, and kill at least one detective. This also serves to make a distinction, however; Neil and his crew take no pleasure in killing, viewing it as an unpleasant but necessary possibility of what they do, while Waingro is sadistic and actively takes pleasure in cruel murder.
One-Scene Wonder: Unusually, it's a one scene pairing. The two lead characters spend the whole movie plotting against one another, but never meet and aren't on screen together except for one great scene where they sit down and have coffee (see Not So Different) and the final showdown. Notable, because it's the first time Pacino and De Niro ever did a scene together.
Additionally, Jeremy Piven shows up as the doctor who treats Chris after the bank heist.
Rooting for the Empire: Neil has quite the following despite being ultimately a bank robber, murderer, and all-around bad guy. This was probably at least partially intentional, though, given the amount of Character Development he gets.
So Cool It's Awesome: Even disregarding the fact that it puts two of the greatest actors in cinematic history onscreen together, it's generally regarded as one of the best cops and robbers movies ever.