Gray and Gray Morality: All of them are generally mild-mannered and approach their job with a commendable level of professionalism (given that their job is mentally dangerous to them as well), but that job does involve searching through people's minds in order to steal important secrets and (in the film's main case) using lies to give someone an idea from the inside.
Meaningful Name: "Cobb" means "dream" in Sanskrit, Hindi, Urdu, and Punjabi. It's also an old English word for "spider" (hence the word "cobweb"). Fitting, for a man who weaves webs and traps others in them.
Older Than They Look: In the middle of the film, he has lived eighty years mentally—by the end, it's unknown how old he is.
The Comically Serious: Arthur is the most level-headed and serious member of the team, and as such is not amused by Eames' somewhat careless behavior, getting his chair constantly tipped over, or loud music.
Critical Research Failure: In-universe example, Arthur fails to find out that Fisher has had mental training to protect his subconscious from infiltration - arguably the most important piece of information needed when planning to infiltrate someone's dream.
Corrupt the Cutie: Professor Miles even refers to Cobb as wanting to "corrupt" one of his best students. Cobb openly tells her the job is not legal, but he, Arthur, and Ariadne herself each admit that after tasting the power of dream architecture, she would never want to go back. She willingly joins The Team.
The Heart: Her status as this helps her to get closer to Dom and realize that he has issues that need resolving.
I Just Want to Be Special: This is essentially what the dream world offers compared to reality and is what Cobb counts on for Ariadne to join the team.
Reality Warper: Only in the dream world, Eames is the "forger" in the team which may explains why he is the most competent member in the team during the execution of the mission. His forging ability allows him to pull out a grenade launcher out of nowhere in the first level, shapeshift in the second level and to a certain extent become a One-Man Army in the third level.
Warrior Therapist: He works out most of Fisher's "problems" before and during the dream. He even sarcastically mentions that he should be getting paid more by Fisher than Saito for the job.
Why Do You Keep Changing Jobs??: He's somehow able to get a job placement in the Fisher company right within their head office to observe Browning. His justification? "References are sort of my specialty."
I'll tell you a riddle. You're waiting for a train, a train that will take you far away. You know where you hope this train will take you, but you don't know for sure. But it doesn't matter. How can it not matter to you where that train will take you?
Dissonant Serenity: When the dream is collapsing and everyone else is running around frantically, what does Mal do? She calmly walks through the destruction and is amused at how Dom gave Saito the wrong documents.
Thanatos Gambit: Mal commits suicide, but makes it look like Cobb murdered her so he'll be compelled to do it with her or lose custody of the children. Of course, like the many characters who kill themselves in dreams in this movie, she doesn't believe she's really dying.
Walking Spoiler: The trailers make it out that she's the Psycho Party Member of sorts, but given the spoilers, she's actually Cobb's wife who killed herself and continued to exist through Cobb's guilt, manifesting into something... unstoppable.
Meaningful Name: Fischer's name may be a reference to the Arthurian legend of the Fisher King, whose kingdom physically changes to parallel his wounds and suffering; this is appropriate given that much of the film takes place within his troubled mental landscape. Also, "Robert Fischer" was the name of the famous chess player.