I knew one, who came from a long line of JW's, many generations in, grandparents and great grandparents who prided themselves as being conscientious objectors, the whole family were and are regular pioneers living a lifestyle totally devoid of material wealth, they are a family of JW's that are considered odd even among JW's, if you can believe such a thing. The eldest son, a regular pioneer to the day he died, when he was around 21 threw himself under a train as it passed the station. They had to use teeth found at the scene to identify the body.
I knew another guy who was chewed up and spat out by the org when I was a kid... He was the 'apostate' that would come to the hall drunk on meeting nights and shout and ball, and the local MS and Elders would try to act macho and get him out of there... I don't know what the whole story was as to why he was so messed up, but in the end he killed himself as well.
When I was a JW, one of my friends sisters, after many many cries for help (attempted suicides) climbed a building with intentions of jumping off it, and when the firemen were trying to talk her down, she fell... or jumped, I guess only she knows which.
I know of other cases but those are the three that stand out most in my mind.