Awesome Music: While the soundtrack as a whole is mostly generic action music, the incredibly bittersweet ''Radio'' may well put a lump in your throat.
Badass Decay: John Connor. Justified, though, by the fact that he'd spent ten years believing he'd escaped his destiny (but still paranoid), and so had not prepared for it and was tranqued up for most of the film.
Some even go so far as to claim only the first two films as canon, and everything else after as either a different timeline or just a dream, with the alternate ending to T2 being the official "end" to the series.
When John asks about Crystal Peak, the T-800 remains silent, letting Kate's father talk about it being safe and not volunteering any information. At no point does the T-800 let on there's no way to shut down Skynet from there. That way, it doesn't have to lie.
Another reason Sarah had herself cremated so that if Judgment Day still happens (as she fears it would), Skynet would not be able to find her remains and use her DNA to make a Terminator resembling her to trick her son, like how the T-1000 tried.
Harsher in Hindsight: At the beginning of the movie, John Connor is living "off the grid" as a drifter, breaks into a veterinary clinic to steal painkillers, and in the process runs into someone he hasn't seen in years who claims that he "just disappeared". Nick Stahl, who played John, disappeared for a period of five days in 2012, avoiding phone calls and getting drugs.
Narm: The scene where the female terminator inflates her breasts to distract a police officer. It's blatant fanservice in a movie series thats not known for fanservice and a huge step down from the T800 and T1000's iconic badass intros.
The female terminator tends to spend alot of time trying to be sexy for a killer robot, as opposed to the previous two models being nightmare inducing killer androids. See in particular the scene where she "analyses" a blood spot by licking and sucking her finger in a pointlessly lengthy and sexualised way.
"Talk to the hand".
Those pink glasses.
Narm Charm: The Terminatrix crashes into the base with her helicopter? Badass. The T-800 follows suit by crashing his too? Hilarious.
Seinfeld Is Unfunny: A female Terminator. Since 2003, fans of the series have gotten so used to the idea that it's now a bit hard to appreciate how novel it was back when T3 first came out. Now, of course, the T-X is inevitably compared to "Cameron" of Terminator: The Sarah Connor Chronicles, who was much better received.
It doesn't help that the former was played by Kristanna Loken (who was largely unknown in 2003, and has had few major film credits since T3), while the latter was played by perennial fanboy favorite Summer Glau (who was already something of a sci-fi icon before 2008, thanks to her role as River Tam in Firefly).