Some interesting choices above. This thread is interesting more as a social experiment to see where people view actions, and is probably more useful as a tool for looking at oneself and one's own moral compass, rather than anything else.
Having said that, here's my take, and therein, an insight into my own moral code:
Paragon Shepard => Neutral Good. He does the good thing, without regard for laws, but still believes in the general order of things. There are moments where he's lawful, and moments where he's chaotic, but he's always generally good, so that must make him generally neutral good.
Renegade Shepard => Chaotic Evil. He's doesn't really give a crap for anyone else's issues, he doesn't give a crap for laws, and he's a bully. His motivation is revenge, power, and to put a stop to whatever's threatening him and his team of lick-spittles. He's wholly self-centered, and will execute anyone who gets in his way (when given the choice).
Mordin => Neutral. This guy is the epitome of Neutral in my opinion. Cold, scientific, calculating, morally ambiguous, doing whatever is necessary to keep balance within the Galaxy, and will fight for whatever cause that prevents the balance from being upset. Science/knowledge is neutral and impartial, and that is how Mordin lives his life.
Samara => Lawful Neutral. She is the ultimate Lawful Neutral character. She lives, dies, kill,. and saves, all according to the code. Her personal feelings about things doesn't even matter. If her code says you must die, then she will kill you. She says that it doesn't matter if someone is a father and killing him may cause more harm, the father must die according to her code. A truly good person would consider the ramifications of their actions and its impact. Samara does not. She's all "code", and this she is not Good.
Grunt => Neutral to Lawful Neutral. Grunt is a hard one to judge. He simply does what he does, and has trouble understanding why he should care about anything. Later in the game he develops a reason to care, but he often refers to Shepard as his BattleMaster and the Normandy's crew as his krannt (family), and thus feels bound by the code of his ancestors and "clan" to serve under Shepard's direction.
Garrus => Chaotic Good. Easy. He's the ME2 equivalent of a dark version of Robin Hood. In ME1 I would've said he was Neutral Good. However, towards the end of ME2, I've used Garrus a fair bit and he rarely balks at ReneShep's more nasty side, so I may lean towards classifying Garrus as Chaotic Neutral.
Jack => Chaotic Evil. About as clear as that one gets. She's out for herself, wholly, and blowing up stations shows zero regard for any innocents on board. She'd be a war criminal monster in any jurisdiction, her background sob story aside. She kills any who gets in her way, without regard or remorse. Don't know how anyone could classify an unrepentant mass-murder as anything but evil in the truest sense.
Morinth => Neutral Evil. Clear as day to me. Wholly concerned with her own self gratification. Kills for pleasure, and justifies it as doing the victim a favor. Evil, evil, evil. She doesn't fancy rules, but she's also no agent of chaos, which makes her just plain evil, or in D&D terms, neutral evil. Unsure how anyone could ever view her as non-evil. Too many suckers falling for her "I'm hard done by" sob-story is my guess.
Jacob => Lawful Good/Neutral. A soldier. Lives and dies by the rules of combat, but wants to do the good thing for humanity as a whole. He distrusts TIM, but sees Cerberus as the best chance he has to continue to do good in the service of a para-miltary unit. His loyalty mission makes it absolutely unambiguous as to where he sits on the moral compass scale. There are rules that simply cannot be broken, and things that you simply don't do, no matter the situation. He's close to about as Lawful as it gets without being a zealot like Samara, but does still ponder about what is the best/right/good thing to do.
Miranda => starts off Lawful Neutral, becomes more Neutral Good by end game. Follows the rules, is a team player, and justifies Cerberus's action as being for the greater good while overlooking the moral ambiguity of it all. Towards the end she learns to stop following orders blindly, and develops a stronger conscience for doing the right/good thing (ParaShep path). Otherwise, remains Lawful Neutral (ReneShep).
Zaeed => Chaotic Evil. Seems fairly obvious. A mercenary bully. His loyalty mission dissolve any notion of goodness where he's willing to sacrifice the lives of the trapped workers for his goals. Selfish monetary interests are the only things that speak to him. The guy is about as close to classic Chaotic Evil as it gets. Too many people seem to confuse Chaotic Evil with Chaotic Stupid, and Zaeed therefore confuses such people. He's not stupid, but there's no shred of goodness in him. He rules with an iron fist and kills without mercy, purely because the money tells him to.
Thane => Lawful Neutral (early life) developing to Neutral/Chaotic Good. He is a "weapon". A gun. He is detached from his body and has no moral perception or consequence during his early life. He follows orders and does what he's told and doesn't question. After his wife dies he goes rogue and tries to do good by killing bad people, almost being identical to Garrus/Archangel in that respect.
Tali => Neutral Good. She does what she has to, for the good of her people, but she's not a zealot.
Legion => Neutral. He/it is a machine, and wants to build consensus for a peaceful co-existence with organic sapient life.
The Illusive Man => Lawful Evil. A well organised businessman who runs a tight ship, and does whatever it takes to see his vision through, no matter the expense to others. He sees himself as the necessary ruthless organised "evil" in order to see that humanity continues to prosper.
Whew, long post. Did I forget anyone?