Here's my guesses.
Rachel- Unhealthy ENFJ
Blaine- I used to think ENFP but now I'm leaning more towards ENFJ. ENFP is still a possibility though.
Mike Chang- ISTJ
Joe- Some type of NF for sure. I think he might be a premature ENFP, just because of his "Everything is possible" mindset and the fact that he seems to bite off more than he can chew.
Rory- I'm thinking an ISFP?
Sugar- oh god. ESxx?
Karofsky- Nothing comes to mind except xxxP.
Will- I refuse to acknowledge him as an INFJ. No idea what he is, but I really hate him.
Burt Hummel- Maybe an ESTP who's developing his Fe...