Everyone's going to have an opinion about that guy.
My hack: He's NF. My twin says he's like living with me and Taco (the "other" ENFJ in our lives), but truly I thought he was maybe ENTP at one point. Granted, that idea went away when I compared him to Craig Ferguson who is so Ne-primary it's crazy.
Conan is a freak who makes me laugh. Whatever he is.
eNFJ 4w3 sx/so 468 tritype
EII-Fi subtype, Ethical/Empath, Delta/Beta
AIS Holland code
INFJ. He's not extroverted (never, ever see him out and about), he's most definitely not a sensor (otherwise I'd never watch him or get his humor), not a thinker ( his reaction to things give that away) and for fucks sake P!? Look at how perfect he looks night after night!! I wish I could get my hair to look that good!
Letterman is probably introverted, certainly a thinker. As for being a sensor/intuitive or judgmental/perceiver I'm really not sure. To guess I'd say INTJ but he could be a P.