You can't. Due to severe blood loss you faint, and wake up in the hospital, saved by a good samaritan.

I chopped my head off with an axe.

Unfortunately that's a lot harder than you thought it was, and all you manage is an ear before you decide it's too much work.

Someone wishes I was dead.

But that wish was stolen by someone else on a differnet rooftop.

A nuke goes off right next to me.

Distance is relative. Considering the size of the universe, right next to you is mars. That's where the nuke went off.

I don't want to set the world on fire, but I did anyway, and now I'm burning up.

However, you managed to do this mere seconds before God flooded the Earth, and you are doused by the massive amount of water pouring down on you. On the plus side, you get saved by Noah when the ark goes floating by.

I've always wanted to fly under my own power. So I jumped off the Sears Tower and plummeted to Earth, smashing head-first into the concrete.

But this is the matrix so you bounce to safety, just like Neo the first time. Everyone falls their first time.

I drink too much water and get water poisoning.

Except that you could no longer control your bladder. You now hold the record for the world's longest pissing of one's self.

Every God in the multiverse has deemed me a threat. They combined their power and kill me in every possible timeline.

...Except this one, which they've completely forgotten about.

I grow old and die of old age.

Except that by that time, modern medicine has figured out a way to not only resurrect the dead, but then make them immortal. You are raised and now can no longer die.

I jump into the mouth of a living, fire-breathing, adult red dragon and proceed to force-feed myself to it.

The dragon finds you so distasteful that it vomits you out, then proceeds to kill itself rather than live with the memory of your flavor

I travel back in time and kill my mother while she's pregnant with me, therefore ceasing to exist.