My standby is the "Why would god send Ghandi to hell?" argument.
Basically that religion is 90% culture and regional. Those that grow up in India, with Hindu friends and family, generally have those beliefs. Same with Muslims, Buddists, Jews, ect. Some of those people of other religions are great people, who spend their entire lives doing nothing but good for others. They make the world better, they feed the hungry, fight oppression and strive for peace. But the Christian god sends them to hell simply based on what culture they were born into. That sort of god is an asshole, who I don't care to spend eternity with anyway.