Two items I'd like to address:

First, why I posted the quote at all.

Some Objectivists find agnosticism objectionable, as it waffles on a basic philosophical question. Likewise, the quote might be seen as objectionable, as it concedes that there may be a god.

What I like about the quote, however, is its spirit. Conventionally, religionists pretend that their god is omnipotent, so that you, having displeased him, are fucked when you're brought before him to be judged. (Cf. just about every Chick tract.)

What appeals to me is the idea that you can defend yourself against god if your weapon is good enough.

Second, attribution.

Ostensibly, the line would seem to be from Kill Bill: Volume 1. It might be credited to the character Hattori Hanzo, to the actor Sonny Chiba, to Sonny Chiba as Hattori Hanzo, or to Quentin Tarantino, who wrote the script.

However, some research reveals that the line did not originate with Tarantino.

http://www.eatmybrains.com/showfeature.php?id=4

The line, "If, on your journey, you should encounter God, God will be cut," which Chiba says to Thurman when he gives her the sword, is lifted straight from Makai Tensho, a bizarre 1981 samurai movie by Kinji Fukusaku also starring Sonny Chiba as well. In the US the film was released on video as Samurai Reincarnation, but didn't do very well commercially as it portrayed the Christian invaders as evil; not something that would be popular with the 80s American market.

To know with whom the concept originated, it would be necessary to know if it was present in the original novel Makai Tensho. Candidates are Futaro Yamada, who wrote it, and Kinji Fukasaku and Tatsuo Nogami, who adapted it for the screen.

http://www.imdb.com/title/tt0082699/fullcredits#writers

As I haven't read the novel, I've given Tarantino credit for this specific English translation of the quote.