"Zat"-gun discrepancies? I've noticed that the zat gun seems to affect different characters in the series differently.  O'Neil, for example, seems barely affected by it, whereas, other characters will be knocked unconscious for long periods of time.

Is this ever explained, or is it assumed that there's a built-up tolerance to the weapon.  I'm about halfway through season 6 of SG1, and it's one of the biggest questions I have yet.  This is the first science fiction television series I've gotten into (except for x-files when the show was originally aired), and I'm REALLY enjoying it thus far.