While its very unlikely (but very possible) my dream in life would be to witness a supernova.
Last time one was bright enough to see with the naked eye was about 400 years ago. So my chances are slim.
Interesting side note, a supernova is the fastest moving stellar event we can see with our naked eye that we know of. It starts and ends (usually resulting in a nebula) over the course of just weeks to months. Could you imagine seeing a bright light form in the sky out of nowhere, last for months, and then in the end have a beautiful new nebula in its place... my god that would be so cool!