Most frustrating Fallacies that Religious people bring up?

[John V]

I think that's the slippery slope fallacy, that assumption when A happens then B will necessarily follow, without having done the research to properly conclude A leads to B.

A famous and fairly recent example was when the fundies were arguing against gay marriage, saying, "if we allow that, next we'll be allowing incest and beastiality and underage marriage, etc."

Another recent example was Bill Nye arguing that a rejection of evolution will lead to losses in all sciences.