I have cried at random movies over the years, but it wasn't until watching Saving Mr. Banks that I cried at a trailer for an upcoming movie!
I saw Saving Mr Banks twice (first time was to see if it was appropriate for my kids), and I cried during both showings at the 'Heaven is for Real' trailer.
My kids want to see that movie when it comes out, but I don't think I'll be able to make it through!