I have to say that for me it has been BSG. Several times now in my complete series rewatch (in chronological order for the most part -- saving The Plan for last, though I did watch Razor in the middle of Season 2) I have found that my allergies or something must have kicked in, or something got in my eyes or whatever. Yeah. Thats it.

Funny part it, it coincided with some sad like stuff on screen, like the deaths of certain characters, or other highly emotional (for the characters, not for me, um, of course!) scenes.

I remember similar eye problems when I watched the series finale to M*A*S*H years ago, and just about everytime since. Even the ending of the series finale for Buffy made me start to tear up, um, I mean, have an allergic reaction. Quantum Leap did that too, during several episodes.