I have to repeat some of the other things said here...
The 4th DBGT Ending (suggested by veshira) - The first time I saw this, the whole animation just tugged at my heartstrings. It was a fitting last ending song for the Dragon Ball series. (If they had "Sabitsuita..." as the music for the flashback montage at the end of DBGT, I think I would've cried harder.)
My Resolution (suggested by Steven Perry) - Okay, so it's a music video, but the music fit so well. Man it gave me goosebumps and I had to pause the video during the first "I'm Already There" line because I was fighting back tears. And of course, it contains the Goku sacrifice episode, which I will list down next...
"Bye-bye Everyone! Goku's Last Teleportation" episode - Goku's last words to everyone (a simple "bye-bye"), his last words to his son ("tell your mother I'm sorry"), and the heartwrenching screams (Gohan's "Otousan!" and Kuririn's "Goku!") - I feel like crying everytime.
"For the sake of the ones I love, Vegeta falls" episode - Same feelings as above, and Kuririn even screams again. ^^;
Aw gosh darn, there are so many, but those are the ones I really remember crying for. And anytime I think about the Dragon Ball characters growing up, I almost always tear up.

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[b]DBZ Movie Trailers![/b]: [url=http://www.youtube.com/watch?v=9Jjm1JU43z0]Namek on Fire[/url] / [url=http://www.youtube.com/watch?v=XyPiWvvKxsk]Resident Evil[/url] / [url=http://www.youtube.com/watch?v=lhMaYs5OGfY]Pirates of the Galaxy[/url]
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