Interesting you get a lot of replies which are basically everyone's personal preferences. Really need more detail on what you want to do....

I like Ubuntu but recently moved to Fedora on one of my machines because it seemed a bit more flexible with multi monitor setups.

Any one of the distros can be made to work.

Do you have reasonably modern hardware? Do you prefer the Gnome desktop or KDE? Do you want to develop? Are you a gamer?

As a newbie, I would go with what is common and well supported. Ubuntu is pretty easy to get help with. Fedora is not hard either.

Fedora does have the "Security Enhanced Linux" turned on by default. It is a little bit of a PITA sometimes but it makes me feel a little more secure on a machine that has outside world connectivity.

What do you want to do with your linux box?
David