Fluke ;_; I'm not the type of person to cry at a movie. In fact, I hardly cry at all. I haven't ever cried at this movie, or any movie, before. But just the last time I watched that, I got teary eyes at the point where Fluke's owner and "mother", Bella, died (she was homeless and sick). I also cried when Rumbo, Fluke's doggy friend who looked after him when Bella died, was shot and killed (although he came back, reincarnated as a squirrel

).
Another one, that I just saw recently, was Flicka. It wasn't a particularly sad movie - not in my eyes, anyway - (except for the fact that real horses died in the making of it) but at times throughout the movie I put myself in the characters' places (dumb as it seems), and that made me cry.
Some people here have mentioned Homeward Bound I and II. The sequel was not a sad movie at all (although there were things like dogs fighting, kids trapped in house fires, dogs attacking humans, guys getting dumped by their "mates" etc...), just a tad too romantic, the first movie made me get a little teary-eyed. I didn't cry when the trio were left behind by their owners. I didn't cry when Sassy was swept down a river. I didn't cry when Shadow and Chance were attacked by a cougar.
I cried when Shadow fell down that hole, and believed he would die because he couldn't climb out.
I have watched that movie many times since I was tiny. Around 5, but probably even younger. I never cried then, possibly because I was young and didn't understand (whenever I cry at movies I always sit there saying "it's not real, it's a movie, it's not real, it's a movie...*) and even now if I watch it again I don't even feel remotely sad, but one time I really saw the emotion in that scene, how Shadow wanted to curl up and die, how the others believed they couldn't go on without him, how Peter (Shadow's owner) convinced himself that Shadow was dead. Sometimes things can seem so real (precisely the movie-maker's ambition

).
* Although, of course, some movies like Eight Below were based off of true stories, so crying there is understandable.
OMG!...I loved Fluke...It makes me cry every time.