The internet is awash with claims made by religious / non-religious groups making claims for specific people: "Einstein is ours!" "Hitler is yours!". I find this really boring, so I thought I'd list some confirmed completely fictional atheists.

In no particular order:

Gregory House, House
There can't be many better TV characters than House, surely? I haven't seen anything like enough of this show, to my shame. Everytime I see it, I decide I'm going to watch much more, but end up being otherwise distracted. His miserable, Sherlock Holmes style genius is just perfect.

Daniel Plainview, There Will Be Blood
If you've not seen this, and dark, brutal, slow-paced movies appeal to you, then you are really missing out. I'm sure there will be lots of people who wouldn't enjoy this, so don't come moaning to me if you don't like it! This was beaten to the Best Picture Oscar by No Country For Old Men in 2008. There Will Be Blood has religion running right through it (like the oil... geddit?), with the miserable, capitalist, atheist Plainview (Daniel Day-Lewis) battling against the faith-healing preacher Eli throughout.

Brian Griffin, Family Guy
The smartest dog ever? This one is really quite interesting. Brian only recent "came out" as an atheist on the show. There have been thousands of blog posts about this, stating things like "Is this the first ever endorsement of atheism on TV?" (presumably American TV...).
Seth McFarlane, the creator of the series, is also an atheist:
"I’m an atheist, not to be a dick, but just cause it seems like the most likely scenario."

Jean-Luc Picard, Star Trek: The Next Generation
Picard was probably the most philisophical character in this very secular minded series. His talks on what it is to be human with the cyborg Commander Data were always a highlight. (The second video is just included for a laugh, of course...)

Mr Big, Sex and the City
I'll be honest, I've never really watched this show, and on the few times I did, didn't really get it. I'm reliably informed that Mr Big is a very important character, who is also extremely successful and smart. He certainly seems an important character, as all the videos I can find with him in also contain the Horse Faced One.

So there we are! Feel free to rip my selection to shreds, or leave your own suggestions below. If I get enough I might do a part 2. Maybe...

This is pretty unbelieveable. Not the most exciting 4 videos ever, but still jaw dropping!