One of the things that can really cause a jolt in a story is the death of a character, when done with the proper situation and timing. Doing this can bring a wave of emotion over the reader, especially if it was not expected.
There are many ways in which you can kill off a character to bring that maximum response that you seek. For example, a minor character can finally come to his own and step up to the plate when he is needed. Finally proving to himself and to the world what he was capable of.
The always familiar 'hero making the ultimate sacrifice' is still a good way to I think. I don't think that it will ever get old. There is just something about sacrificing one's self that brings that emotion out. After all there aren't many greater things that one can do.
The same can also be true for the death of that final great evil. Making a final death both original and spectacular can be very difficult but is definitely worth it. I mean everyone remembers when the Death Star was destroyed and I haven't seen that movie for more than ten years.
Something that I sometimes like to do is create a character for the simple purpose of being killed. It may sound bad but getting to know a soldier who is about to give his life can only be a plus in my book. You can get to know why he fights and get deep inside his head as the scene is onfolding. When he finally dies his death means a lot more at that point. I like this strategy in particular for writing about a tragedy or ill fated mission.
One of the things that I don't particularly like is the false death or 'warrior returning alive'. That is when someone you thought was dead returns later on to play a pivotal role. If you can pull this off then by all means make the most of it but it has been done so many times that it would have to be something really special to make it stand out.
All in all, killing characters can be a good thing whether to spur on a hero or just to keep things fresh or interesting. You just have to make sure you do it right.