Cap'n Kobold
Hero
Arguably being able to observe the direct actions of deities makes them far more open to criticism.
"I don't follow any God, they're all jerks!"
Blood of Vol then.

Although its worth noting that in terms of language, the PHB uses "god" and "deity" pretty interchangeably to mean "religion or philosophy that your character follows" rather than an actual entity. I.e. the Blood of Vol is a philosophy, but is still considered a "deity" in those terms.
So a Cleric of "War" is still considered to have a deity even though her beliefs are secular. She could prepare any area strongly associated with war, such as an armoury, strategy room, barracks or sparring area as her sanctuary.
Pretty much everyone in Eberron believes that there are gods though. There might be no proof for the Sovereign Host, or they might be viewed with disfavour, but their existence isn't generally a matter for debate. If nothing else, there is a great gout of silver flame continually burning in Flamekeep as a physical reminder of divine forces at work.Unless, of course, you're playing in a D&D world where physical proof of their existence is lacking. Like, say, Eberron.