Personally, I dont see how anyone killing themselves willingly can be considered "selfish", since the definition is about concern for yourself and your own pleasure only. I have worked with a lot of people who feel suicidal and as others have said they are absolutely not thinking rationally or able to consider consequences to others, so they cannot be considered 'selfish' as they can't weigh up options at that point. In fact most people say that they want to die because they feel they are a burden to others, have no purpose or hope for the future etc, and that others will be better off without them, so they feel they are doing everyone around them a favour by dying.
In case of a violent/public suicide, I guess it is possible that a very few people may decide to 'go out with a bang' but mostly it would be because they want a sure fire way to ensure they will die, many people who feel suicidal will say their biggest fear about the act is not death itself but that they will 'screw it up' and not actually kill themselves. So a jump in front of a train, or off a large bridge, is pretty certain to do this.
A lot of people will have been affected by suicide and I hope that should anyone in that situation read this thread, they will not be upset by people considering their loved ones to be 'selfish'.