At the end of Illuminations. Every. Single. Time.
Sometimes at the end of Fantasmic.
Always when we say goodbye to our hotel, doubly so if we're at Pop.
On the Magic Express, when we cross out of Walt Disney World into "the real world." I cry my eyes out like somebody told me my dog died. Without fail.
The only thing I've gotten better at is not being so obvious about it. Don't talk, look out the window, sneeze beforehand so people think it's allergies. Then let the waterworks flow.
I also may have cried when we met Anna and Elsa, but I had good reason. It was after the Enchanted 10k, I was sore, tired, and it was a relief to finally get in. But more importantly, my son is in love with Elsa. He insists they're getting married. When he saw her, he froze up, blushed, and wouldn't talk to her he was so shy... Which is something that had never, ever, ever, EVER happened to my son, before or since. It was funny, because she invited him to her castle to build snowmen and drink cocoa, he looked at her, said "Ok, sounds good" grabbed her hand and went to go out the door. Nevermind the 8 hours worth of people behind us, he just was ready to go. LoL!