You. At any given point in time, you do not exist. You and your thoughts do not have a physical representation. Your body does show what you control, but not you exactly. You are merely an electro-chemical processing of you by your brain. Every few milliseconds, a new version of you is created, and then destroyed. By the time it takes you to finish this sentence, you would have been created hundreds or thousands of times. And at a certain point in your life, your body will no longer be physically capable of creating more versions of you. Your physical body will stay in this world, decomposing until it's just the calcium in the bones that's left. But you won't be here. Your final version of you will be destroyed. You... will seize to exist. As Banksy once said, "They say you die twice. One time when you stop breathing, and a second time, a bit later on, when somebody says your name for the last time."
I love how every time I'm serious on this server, someone has been thinking about this longer than me.
Weird shit, apparently (o.o; ) TNT, you need to slow down on Undertale, and go home, you're drunk, or just really messed up...
I technically meant your thoughts aren't physical. Instead, your conscious is made by chemicals and electricity.