As a manly man, I have a real hard time crying. That lump tries to squeeze out of my throat and gets stuck. My eyes try to well up and I get a severe case of post-sadness headache. Needless to say, I was in pain when Sheridan and Delenn said goodbye and was extremely thankful when the commercial came in and gave us a break. My wife was crying all over the place, and she only watched B5 to humor me.
(She was won over though. Halfway through re-watching Season 2 on the DVD's she announced G'Kar as her favorite character. I already knew.)
I didn't well up over the destruction of B5. By that time I was simply silent and marveling at that glorious hour of sweet sadness in its entirety.
There's only a handful of scenes that make me tear up, and I just don't know what makes them stand out. Offhand, I can only think a few:
The Patriot: Mel Gibson goes to leave on horse. Little girl cries, "Papa!" (She then spoils it by rambling on "I'll say anything!", but hey)
Jumanji: Can you believe it? I was watching this over the weekend, and from the time Robin Williams is running around the house looking for his parents until he visits their graves, I'm choked to the eyeballs. Ouch! And I already KNOW it's all going to turn out alright in the end! Speaking of, I choke up again when the game is over and his dad comes back in the room. F***ing James Horner music!
I got choked up watching the movie "The Seventh Sign", at the very end when Demi Moore and Michael Biehn's baby cries, signifying it was not stillborn (WILL YOU DIE FOR HIM?). Of course, I was a new father back them. It might still work though, I haven't tried it.
The TNG episode "The Inner Light" got me the first time, but not nearly as much afterward. Next to SiL, it's probably the best sci-fi tearjerker out there.