A disabled former Marine who becomes part of the Avatar Program after his twin brother is killed. His military background helps the Na'vi warriors relate to him.
Backup Twin: What kicks off the film. Jake is on Pandora because his deceased brother was involved in the Avatar program, but now that he's dead only his genetically identical twin can use his Na'Vi body.
Becoming the Mask: And how! The last line you hear is his narration "I can't be late to my own party. After all, it's my birthday." He means he will be joined to his Avatar permanently.
Specifically, a Call Back to the Navi belief that every member of their clan is born twice. The second time is when they join the clan. Jake's second birth was permanently swapping bodies, as well as becoming a full member of the clan.
Honor Before Reason: Lampshaded. "We're going up against gunships with bows and arrows... and I was hoping for a plan that didn't involve matyrdom."
I Just Want to Be Badass: Part of Jake's motivation. It starts as I Just Want to Be Normal (restoring his legs back to healthy condition), but Jake is implied to have been a pretty badass marine before his crippling wound, and embraces the life of a Na'vi hunter/warrior very quickly.
Jake's departed twin's name was Tom, or Thomas - which means 'the twin.'
Sully is also meaningful, regarding the human actions on Pandora.
Messianic Archetype: Jake uses a legend he heard to tame a dragon and become this in Na'vi eyes. It's implied that this is what all the previous "messiahs" did as well: They knew they needed to unite their people, so instead of sitting around waiting for their goddess to do it for them, they did the one thing they knew would get everyone's attention.
Mighty Whitey: Whether it is subverted or played straight is subject to some debate.
Took a Level in Badass: Jake takes about ten levels during the movie, going from poking Pandoran flora just for the hell of it to riding the moon's biggest aerial predator and taking out two huge gunships, almost single-handedly. It's possible that he is simply restoring his badass levels from his human life - he used to be a tough marine who served in Venezuela before his spinal injury left him wheelchair-bound.
What Happened to the Mouse?: Jake jumps off his Banshee, which has paired with him for life, to catch a bigger ride. His Banshee is never seen again for the remainder of the film. Made even more obvious by Neytiri's obvious distress at the death of her own Banshee later in the film. At the end Jake narrates that the Toruk Makto is no longer needed, and indeed the Toruk is shown flying away. Jake probably "explained" the plan to his Banshee ("You're not gonna like this...") and they reunited after Toruk left.
That's what's implied at the end of the film when the Toruk flies away without a rider.
Your Approval Fills Me with Shame: Col. Quaritch thanks Jake for giving him a perfect excuse to blast the Na'vi and their tree to smithereens. Naturally, Jake is not amused.
An exobiologist and head of the Avatar Program. She is also Sully's mentor and an advocate of peaceful relations with the Na'vi, having set up a school to teach them English.
Actor Allusion: The character played by Sigourney Weaver was called Shipley in earlier drafts. She spends a lot of time in a capsule, is pretty badass and no-nonsense, and knows a lot about extraterrestrial life forms. Are we being told something?
You Monster!: Grace calls Selfridge one when Quaritch destroys Hometree.
Dr. Norm Spellman
Played By: Joel David Moore
A xenoanthropologist who studies plant and animal life as part of the Avatar Program. He arrives on Pandora at the same time as Sully and operates an avatar. Although he is expected to lead the diplomatic contact with the Na'vi, it turns out that Jake has the personality better suited to win the natives' respect.
The Rival: Norm understandably feels this way at the beginning, when he, the Ph.D who's spent years studying Na'vi culture and the Avatar program, gets showed up by the unschooled, last-minute replacement jarhead. Eventually, he puts the research above his own ego and assists Jake.
A scientist who works in the Avatar Program and comes to support Jake's rebellion against the RDA.
Played By: Giovanni Ribisi
The corporate administrator for the RDA mining operation.
Corrupt Corporate Executive: Parker Selfridge. The only reason he didn't want to initially genocide the natives is he was afraid of a publicity backlash, though he is quite visibly disturbed by Hometree's destruction.
Mr. Exposition: Selfridge explains to Grace why they're on Pandora - the $20m/kg Unobtanium. Of course Grace would already know this, yet she doesn't tell him to stop treating her like an imbecile. It's probably more of a sarcastic reminder that unobtanium is the only reason Grace gets to do what she does, so she shouldn't neglect it. It's condescending, but still reasonable for someone to take such a tone in real life.
My God, What Have I Done?: Not stated, but implied with a few instances of Parker feeling some slight guilt over the actions he's taken. Watching on a monitor, He's forced to look away at the bloodshed of the final battle and Grace and Jake get through to him enough that he allows them a final chance to negotiate peace before they destroy Hometree.
Office Golf: Selfridge does this, despite being on a moon where they probably don't make golf clubs. He probably did have it made on-world, given how insanely expensive interstellar travel is. Or alternatively, he is simply self-obsessed enough to have brought them there with him despite the cost.
Smug Snake: Honestly, guy seems completely oblivious (quite possibly willfully) to anything that doesn't have metaphorical dollar signs painted on it. To the greedy bastard's credit, his humanity finally bled through when Grace reminded him that Quaritch was going to kill babies if he doesn't stop the bloodthirsty general, and showed genuine horror and sadness when Quaritch did, but was absolutely powerless to stop it from happening.
Colonel Miles Quaritch
Played by: Stephen Lang
The head of the mining operation's security detail. Fiercely loyal to his military code, he has a profound disregard for Pandora's inhabitants that is evident in both his actions and his language.
Anti-Villain: He's willing to destroy massive amounts of Pandora to get the unobotonium to save earth and humanity.
Armies Are Evil: The SecOps troops are a private security detail retained by RDA, but many of the same aspects apply, and they are obviously meant to draw parallels with Blackwater (now Xe).
Big Bad: The ultimate antagonist of the story, even taking all of Selfridge's power over the mining.
Blood Knight: The good Colonel seems to love combat as much as the Na'vi. For about the half of the movie, he keeps talking about going to war. You can feel the tension between Selfridge, who is going for a peaceful solution, and Quaritch, who very obviously resents being kept on a leash and is looking for an excuse for some good old violence.
Colonel Kilgore: Of course. It helps that the character was based off him. Right down to the casual coffee-drinking while leading an airstrike against the Na'vi's home.
Determinator: Quaritch never gives up, not even when he's on fire, lacks breathable air, or when all the other soldiers have been killed and he's the last of them standing.
Dissonant Serenity: During the attack on Hometree, while incendiary missiles are going off left and right and Na'vi are being slaughtered, Quaritch calmly observes the carnage from the flight deck of his gunship, enjoying a steaming cup of coffee.
Dragon-in-Chief: Selfridge may be nominally in charge, but Quaritch is the biggest threat, and by the end of the movie he's effectively calling all the shots on the human side - and it's clear they both know it.
A Father to His Men: Zig-zagged. He's seen as genuinely caring for his men right from the get go with an impassioned speech of "It's my job to keep you alive... I will not succeed." with genuine remorse. He's also sincere in his offer to get Jake's legs fixed and is respectful of his men, cautioning them, congratulating them, and never resorting to using them as throwaway pawns. Of course, besides sentimental reasons, he has very practical reasons for this as well: he's not getting any reinforcements for several years to come. Every soldier lost is gone for good. Having good relations with your men in such situation means a difference between life and death.
Subverted in that when informed most of his men have been killed or are retreating, he reacts with annoyance rather than being upset.
Fearsome Foot: The first scene of the Colonel is an establishing shot of his combat boots striding purposefully towards the main window of Hell's Kitchen (Hell's Gate's main cafeteria/briefing area) as he addresses the new recruits.
Incendiary Exponent: Quaritch climbing into his AMP suit inside of the crashing Dragon gunship with everything on fire. Including his shoulder.
It's Raining Men: Bails out of a burning gunship while inside an AMP suit that has no parachute, landing thrusters or shock absorbers, yet lands on its feet none the worse for wear.
Knife Nut: He keeps a AMP suit sized combat knife in a quick draw position on his AMP suit as a back up weapon. Pandorapedia states this is an optional feature, as well as having shades of Awesome, but Impractical/Rule of Cool about its design in-universe.
Large Ham: A bit. It's Stephen Lang, so it's not unheard of.
Made of Iron: Survives being set on fire and dropping out of a burning gunship to land feet-first in his AMP suit.
Action Girl: Pretty much every female Na'vi except Mo'at - who may have been one in her younger years.
Aliens Speaking English: Justified, since the younger Omatikaya learned English at Grace's school; also, the Avatar drivers have studied, or are studying, Na'vi.
All Genes Are Codominant: The avatars look mostly like the Na'vi, but have five-fingered hands and smaller eyes like humans. Grace has a human style nose and possibly smaller ears (hard to get a clear sighting), presumably as she was one of the first successful Avatars created. Also male Na'vi have hard ridges at the base of their sternum in the middle of their chests, while Jake retains his human-shaped chest in his Avatar form. They may have just started with Na'vi genes and done the minimum amount of tinkering needed to make them into something that a human would feel comfortable in. That would mean five fingers and eyes similar enough to normal human ones that a human could process the input from them.
Bishie Sparkle: The Na'vi have bioluminescent 'sparkles' on their body (see the picture of Neytiri for the example).
Brain Uploading: Personalities of Na'vi, and humans, can be uploaded into the lunar consciousness from within the sacred groves. Downloading into a new body is also possible, but we don't know how common. Large numbers of other Na'vi chant during the upload ceremony, although this seems no more necessary than, say, chanting while backing up your iPod. Unless all of the chanting Na'vi that are noticeably linked into the local network are acting as parallel-proccessing units and local storage. While the global network is big, it's also spread out over the entire moon; having the wetware locally available to act as buffer storage and additional processing during an upload would be pretty handy — especially if you're doing a transfer.
Con Lang: Cameron hired an USC linguist to invent the Na'vi language, then let the actors endure boot camps and line-by-line rehearsals over and over again to learn to speak it flawlessly.
Death Course: The Na'vi education system as experienced by Jake includes a lot of running and jumping in absurdly high places without safety nets or harnesses.
Death Glare: Jake gets a nice long one from almost everyone in the Omaticaya tribe during his first night at Hometree.
Friend to All Living Things: The Na'vi to the flora and fauna of Pandora. They are even able to neural link with them. Doesn't stop some of the flora and fauna from trying to kill them—nor does it stop them from killing said flora/fauna. They just apologize to it afterwards.
Goal-Oriented Evolution: The Na'vi are "more evolutionarily advanced" than humans (according to tie-in media), implying that evolutionary processes have 'levels', rather than just... results. Could also be taken to describe the level of integration with their surroundings (even if this wasn't intended, it still seems to hold). However it happened, they did evolve the ability to link into wildlife like Neo plugs into the Matrix, so one could argue an extreme amount of adaptation to their environment could qualify.
Half-Human Hybrid: The Avatars, specially built to be a hybrid of Na'vi and an individual human's DNA.
Humanoid Aliens: In a meticulously designed alien ecosystem full of truly bizarre creatures - for example, giant six-legged blue horses who drink plant nectar - the Na'vi are strongly humanoid, despite their otherwise Bizarre Alien Biology.
Magic Skirt: The Na'vi tend to wear nothing but a skimpy loincloth. There are improbably few wardrobe malfunctions.
Noble Savage: Played straight, but justifiable as it is not Sully's status as a human (or Half-Human Hybrid) that makes him "Special" but rather, his different cultural background allows him to view things from a different perspective.
Non-Mammal Mammaries: The original Na'vi concept art envisioned a reptilian-like species - at this point, James Cameron said "Right from the beginning I said, 'She's got to have tits,' even though that makes no sense because her race, the Na'vi, aren't placental mammals." However, averted in that the final design of the Na'vi are mammalian, unlike the early concept art◊.
Nubile Savage: Only Jake ever gets dirty, and only because he's inexperienced. Every Na'vi has perfect teeth and skin.
Only Six Faces: Definitely averted. There are CG cartoons that can't seem to avert having most background characters or stars with extremely similar features, but most of the Na'vi all look as different as humans would. Except they're all blue. This is probably because the Na'vi, while CGI, are based on actual actors, particularly in that the Avatars look particularly like their human counterparts.
Serkis Folk: Every Na'vi and Avatar to appear onscreen.
Thong of Shielding: The loincloths basically don't cover their rears at all. Of course, since we see Jake's butt completely unobstructed when it's hanging out of his hospital gown, I guess Na'vi butts just don't count.
Translation Convention: Averted. When Na'vi are talking among themselves, even ones who speak acceptable English, they speak in Na'vi (and we don't always get subtitles, only for critically important lines, although all the Na'vi lines are understandable to a speaker of the language). When Jake is speaking to the elders and to other clans, and it's really, really important, he asks Tsu'tey to translate for him.
Unusual User Interface: The Na'vi's tool of communicating with the creatures and the Tree works like a tentacle-y USB.
The daughter of the leader of the Omaticaya (the Na'vi clan central to the story). She is attracted to Jake because of his bravery, though frustrated with him for what she sees as his naivetÚ and stupidity.