Man is a Religious Animal. He is the only Religious Animal. He is the only animal that has the True Religion - several of them. He is the only animal that loves his neighbor as himself and cuts his throat if his theology isn't straight. He has made a graveyard of the globe in trying his honest best to smooth his brother's path to happiness and heaven. ~Mark Twain
I like this one

Mine are
"I contend that we are both atheists. I just believe in one fewer god than you do. When you understand why you dismiss all the other possible gods, you will understand why I dismiss yours." -Stephen Roberts
"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." -Stephen Hawking
"Philosophy is questions that may never be answered. Religion is answers that may never be questioned." - Anonymous
"It's not that we are better than the universe,
We're a part of the universe,
we are in the universe,
& the universe is in us"
- Neil deGrasse Tyson, Astrophysicist
"The most incomprehensible property of the universe is that it is so comprehensible"
- Albert Einstein
"If Atheism is a religion, then health is a disease!" -Clark Adams
And the one in my sig already
"Morality is doing right, no matter what you are told. Religion is doing what you are told, no matter what is right." -HL Mencken