First, let me loosen the map of the problematic a little because I am not sure that a black hole or a planet would stay completely unnoticed until the end. In other words, I wouldn't be the only one to know. What if the Vogon Constructor Fleet is coming and there is no Ford Perfect around? Lol, sorry for the digression and back to businesses.
Okay. We're talking about the end of the friggin world, here! Nothing could make me loose such a show of my own free will. Not even the chance to fulfill my dearest and darkest fetish. So, what would I do? I am not a special person, so I wouldn't do anything special.
At first, I would pay a last visit to those who I love. I may even try to warn them but I fear to know how it would go. After all, the end of the world was announced in vain far too many times.
Then my plan would be pretty trivial. If the weather was fine, I would camp on a meadow in the countryside and I would wait the end while eating, drinking and listening to music. Alone. If the weather was a bitch, I would do the very same things but in my living room. May be the networks understand what it's happening and set up some nice live news short before the end!