I have a dark and dirty secret: I actually like "Nightwalkers"
It makes no sense: Usually I hate the NID stuff, it had neither my favourite nor my second favourite character in it (not even my third favourite )but I think it´s the only X-filish episode which ever really worked. Maybe because it seemed not to take itself to earnest. And Sam, Teal´c and Jonas had a surprising good chemistry in this episode. Maybe because they seemed to have really much fun with it.