It's a really simple question that can take a person off guard. Even if it doesn't take you off guard, it is a question worth pondering. After all death comes to all. Even the immortals will have to face the heat death of the universe. Consciousness may even prevail through that. That's what I was pondering here.
Your last moment could be more important that your birth. After all you didn't come to this world being fully conscious. But at the moment of your death, there is a good chance that you can be awake and intellectually and spiritually capable. When you are reading this article, you certainly are intellectually and spiritually capable and my question is what if you die right now like the animator from Monty Python and the Holy Grail (1975)
A Super Powerful Being Gives You 60 Seconds To Live
This is another scenario to turn yourself into your own guinea pig. You could also thing of a trap from Saw movies or just somebody write you name on a Death Note and you have 40 seconds till you die from a heart attack. How would you react to this?
Anger won't help. Confusion will serve no purpose. Sadness will not make anything better. Each will feel their own feelings. It could be fear of loss. If you are really depressed and physically hurt, maybe you'd welcome death. Maybe you'd think it's better to be gone so that others will know your value when you are gone. There are so many things to think about.
As A Regular Exercise/Meditation
Don't plan these things. Just suddenly out of nowhere randomly imagine yourself about to die. There are other variations of meditating on death. I've touched this subject previously in these two articles. You can give them a read:
Life - Death - Meditation
A Companion Piece to Death Meditation
See yourself revealed in those moments. You don't have to tell your experiences to anyone. Just have introspection and try to think why you thought of certain things. You are doing a simulation. So ask yourself if you'd be OK if you really did die in that moment. If you are not happy about those sudden death moments you simulated, maybe you should change something about your life.
It's A Habit
When we make quick instinctual decisions, they are habits in one way or another. When a tree is leaning towards one side, it is likely that the tree falls on the side it was leaning toward. Your habits and your innermost values and principles will be the primary deciding factor of your last moments. Don't take my word for it. Just honestly try this exercise/meditation/simulation and you'll realize.
Do no harm
Do good when you can
Get smart. Get really really smart to know which is good and which isn't.
This is a Reply I made to a comment by 
Just Be Kind
It's a pleasant and positive thought. It's an easy though stream to get in during a point where fear and confusion can easily take over. It's a blameless form of spiritual thoughts. When nothing is going to change your death should you really focus on the world or your achievement or your ideas or should you face your final moments with a pleasant smile.
When a sad face, an angry face or a broken face or even an ambitious face isn't going to change anything, I'd say go for the most beautiful final moment you can think of. Nobody might have any clue about what went in your mind. But you are not going to be dealing with these people's opinions anyways. Be someone who can die without regrets and then die without regrets.
Thought of the Day #1: What If You are Immortal...
Thought of the Day #2: All Of Actions, Their Consequences and The Complete Lack Of Awareness
Thought of the Day #3: What is Good for The World is Good For You - War, Peace, Taxation, Wealth and Innovation With A Touch of Non-Duality
Thought of the Day #4: About Time, Relativity and Lifespan + Pondering Buddhist Cosmology
Thought of the Day #5: What If "God" Was A Self Delusion?