The Newsman, Gonzo, Beaker & Bunsen as the top choices. Of course I like Kermit, and I've grown to enjoy Piggy, which I never thought would happen! Big Mean Carl never fails to crack me up, and Sweetums is adorable.
On SST, Grover and Bert & Ernie.
Films: Aughra (hope I spelled that right) in Dark Crystal, and the Skeksis. The biters-on-sticks scene in Labyrinth has made me flop over laughing every time I've seen it.
Haven't seen enough of Muppets Tonight or Fraggle Rock to choose favorites there.