Close between Zap, Fry and Scruffy.

There isn't one single character that is my favorite. It's the way they all interact with each other that makes the show memorable.

You neutrals sicken me! With enemies you know where they stand, but with neutrals, there's no telling!

I have no strong feelings one way or the other.

(beaten sort of by D21)  But seriously, Futurama is about the sum of its parts more than any single character to me at least.  If I really had to choose one of the more main characters it'd be Professor Farnsworth.

Farnsworth and Zoidberg

Oh. I also like the Brain balls...

They've got a lot of brains and they've got a lot of chutzpah!

Jack Johnson.....no, on second thought, I gotta go with John Jackson......damn, I can't decide!!

The whole crew of Futurama, even the janitor, which we don't see much of. 

Oh god... it's a tossup between the professor and Bender.