Oof, that's hard. On one hand how could it be anybody but Bender, but on the other hand I want to say Kif or Nibbler or Roberto or Lrrr or the Grand Midwife, but when I met Billy West at a convention I bought a Zoidberg picture for him to sign so I guess I have to say Zapp.

Billy West seems like a fun guy :p Leela is my favorite but Kiff is a close second :p

(not an endorsement)