If you were Lord Voldemort and you had a chance to time travel once, what would you change?

The obvious choice is to keep the past version of myself from murdering the Potters. None of this self-fulfilling prophecy crap, just let the Potters get knocked off by some other Death Eater. Shouldn't be too difficult to explain to the past version of myself the consequences of going off and murdering the Potters. And afterward, have the past version of myself use me to make the final horcrux - it's one heck of a significant Avada Kedavra, after all, and I might just survive it anyway.

Convince the real time Voldemort to disarm Draco in the time between Dumbledore's death and Harry coming to Malfoy Manor. Or confund Voldemort to do that or force Draco to make another mistake so that Voldemort kills him. It's better if Draco's only disarmed because then Harry can be under the belief that he's the owner of the Elder Wand. So the story won't change only Voldemort wins the final duel.

If I were a time traveling Voldemort, I would go back in time and prevent myself hearing the prophecy - most probably by killing Snape. For Voldemort, things start falling apart when he hears the half prophecy from Snape and based on his limited understanding (which he does not seek to complete), sets out to kill Harry. Acting on the prophecy gave it meaning and hence it came true. According to Dumbledore - prophecies are often self fulfilling. Not all prophecies ever made come true. The reason being that often, the people involved with the prophecies do not know of them and hence do not act accordingly. In Harry and Voldemort's case, the prophecy becomes important and central only because Voldemort chooses to act on it. If he had not acted, he would probably have not created his own opponent and given him the powers required to finish Voldemort. In Dumbledore's words - "the prophecy is significant only because you and Voldemort choose to make it so. If you both chose to walk away, you could both live!" But because Voldemort chooses to act, kills Harry's parents, gives Harry not only the protection of Lily's love but also instills in Harry a deep seated desire to revenge, to finish Voldemort, to restore balance to the wizarding world and to prevent more children from being orphaned under Voldermort's tyrannical regime. If Voldemort had not heard the prophecy, he would have carried on with his rise to power, never attacked Harry's family, never have the killing curse rebounded on himself, thus ending his first attempt to seize control and also setting the course for the rest of the events that transpired. Things could have ended very differently for the wizarding world with an invincible, immortal Voldermort and no one who has the powers and is destined to finish his regime.

I would persuade vain young Tom Riddle to turn less ceremonial objects into horcruxes. Read more here:

Thanks for the A2A! If i was Lord Voldemort, I'd probably apparate to my 11 year old self and slap some sense into that little crazy kid. I mean, to go to all that trouble of seven horcruxes, and death and revival, to end up being killed by own curse and lose your nose, just cause of a damn prophecy. Hell no..!! I'm keeping my nose, and my life, and become the greatest wizard ever.!! :D ---------------------------------------------------------------------------------------------------------------- Or, in my attempts to fix my life i could mess up the timeline somehow, and cause events that result in the end of the world (Just like Barry did in,http://en.wikipedia.org/wiki/Justice_League:_The_Flashpoint_Paradox). That would be kinda awkward. :/

I would go back and kill Snape. He was the main reason for my death. That snivelly two-timing bastard. Note: This answer is from Voldemort's point-of-view. I have to be evil!!!!

Directly in the words of me(Voldemort) "Killing Lilly Potter was my biggest mistake. If I get to time travel I will push her aside and directly attack Harry".

I'll go to the Garden of Eden and bitchslap hard Eve for eating the Forbidden fruit from the Tree of Knowledge and making Adam eat it too.

I would not kill Harry Potter parents or try to kill Harry. Just go back to the time it happened and warned myself not to do it.