Leslie is an ENFJ. Most people confuse her and think she's either an ENFP or an ESFJ, but she's clearly an ENFJ to me. Extremely goal-driven and too abstract/metaphorical to be an ESFJ. Everything she thinks is about connections and such, and her Ni can sometimes make she sounds like a Te-dom (some people think she's one!). She's too scared of last-minute chages to be an ENFP, but envisions a different future, just like a Ni dom/aux would.
I've always thought Ben was an ISTJ, but I'm starting to think he's an INTP. He's lots of hobbies and different interests for a Te-user and, by the last seasons, he acts probably like the opposite of a Si-dom. His awkwardness, by the way, are nothing like a xSxJ. Also, we're able to see how greatfully his Fe grows because of Leslie.
I really don't know what type Ann is, althought I'd say a very weak, not developed well enough INFJ.
Chris is basically impossible to type.
Ron is an ISTP sp. That's how I see him!
Tom is an ENFP, always coming up with ideas, very emotional and focused on his own feelings. Most ENFPs give a sensor's vibe, so, there it is.
At first I thought April was an INTP, which was a very weird mistake of mine; she's an ISFP. The "cold, no-feeling" vibe she gives off is obviously very intentional and worked on. Also, from what I've observed, most ISFPs are greatly in touch with their Ni, which makes us think they're intuive.
I think Andy is an ESFP.