The person (or persons) who first brewed Beer. This has an advantage that beer was most probability discovered/brewed independently by a number of different people in different locations.

JFK...want to go back and save his life. I believe our world would be very different today if he was not assassinated.

1.) As a proud German I would love to meet Claus Schenk Graf von Stauffenberg in the past and help him to assassinate Hitler succesfully
2.) Carolus Magnus, basically founder of todays Europe. Must´ve had an amazing personality
3.) Jesus, would love to know whether Dan Brown was right about his liaison with Maria Magdalena or not.

hmmm.....Jesus, Moses, Buddha, Sun Tzu, Lao Tzu, Pliny, Livy, Isaac Newton, Leonardo Da Vinci, Alexander Hamilton....

Noobs.

There is only 1. Christopher Hitchens.

And you're quite wrong. Nice try though.

Henry VIII
Elizabeth I
Cleopatra
Jesus Christ
Blackbeard
General Custer
Tutankhamun
Albert Einstein
Leonardo Da Vinci

Now there's a final table! Blackbeard might be 3-betting Christ a little light, I reckon!

William The Conqueror
Henry VIII
Martin Luther
Napoleon
Michael Collins
Wolfe Tone

I'd hope you'd go with someone a bit quicker on the trigger than Stauffenberg. While he was dedicated to going through with the plan once execution began (he was all-in so falling back was not an option anyway), he was part of a group that dithered for too long. I'd probably prefer to go meet Hindenburg in '32-33 instead or a group of General Staff officers in the '33-39 period if this is really your goal. By '44 the damage to Germany and the world was already wrought.

Mohammad. May be the most influential person in history.

I would like to meet my grandfather

Me too, in fact. Was he that good (or bad) the myths are telling?

FDR
JFK
Abe Lincoln
Erwin Rommel
Stonewall Jackson
Robert E Lee
Saddam Hussein
Ruhollah Khomeini
Alexander The Great
Adolf Hitler
Harry Truman
Genghis Khan
Ivan IV
Mohandis Ghandi
Jesus Christ
Abū al-Qāsim Muḥammad aka Moḥammad ( the Islam prophet dude )
Cleopatra
Joan of Arc

Its a big list but So so many intriguing figures each that have shaped the world we live in today, I could only imagine what it would be like sitting in a room having dinner with all the above mentioned. Like sort of Bill and Teds wild adventure thing