I've wanted to discuss this for SO long! Let's get it going, shall we? I'm not even going to preface anything!
Aaron Hotchner - INTJ. He has a lot of Te and it's often used to express what his Ni has noticed. He is also very goal-oriented and constantly has a plan. He is cold and not much fun. Seems very INTJ-ish to me.
David Rossi - ExTJ. I can't decide if he's an intuitive or a sensor, but the rest is all fairly obvious to me. Prentiss describes him as a "fussy, anal retentive neat feak," and describes how organized and specific his notes are. The Te is very clear, and his strong Te is why he is frequently seen cooperating with Hotch. I lean toward him being a sensor. He is clearly an extrovert.
Derek Morgan - ESTP. The badass of the group! He's hands on, suave, talkative, genuine, and great with people. He's observant and witty. Morgan is one of my favorite members of the team because he is so charming. I will not accept him as an ENTP; if you have him typed as such, I'd be interested in hearing why.
Dr. Spencer Reid - INTP. The most blatant INTP in existence. I don't even need to make an argument for this. I've seen him typed as INTJ before and it simply isn't so! He is definitely TiNe, not the inverse opposite.
Emily Prentiss - ExFJ. I literally have no clue on this one. I want to type her as an ESFJ, but I can't imagine an ESFJ doing her sort of job. Whatever she is, the Fe is pretty apparent to me. She wants desperately to be liked and accepted... that screams of Fe. She's also very loyal.
Penelope Garcia - INFJ. Another blatant one. She strives to be unique and an individual. She is sensitive. Her Fe shines through often. She is weird and appreciates weirdness. She's very smart. I don't think much of an argument needs to be made here. Obvious INFJ is obvious.
Jennifer Jareau - ESFJ. Could her character get ANYMORE boring? I have no idea what to type her. I remember in the first two episodes I watched I was thinking she was an INFP. How wrong I was! Maybe JJ fans can help me out here. Out of all the people in the group, she is definitely the strongest sensor, so I don't think I'd accept an intuitive typing.