Who from history would you invite to dinner?

Who the hell is that?

Emperor Constantine?

Probably single handedly made Christianity what it is today. Edict of Milan, Council of Nicaea. He still worshipped pagan deities but knew that unification of christianity was the best way to control the people.
Toss up between Winston Churchill (regardless of his personal politics I'd just love to talk to the man) and Lucius Quinctius Cincinnatus.
Allison Krause (the first one) or Lucrezia Borgia.

I'm guessing you mean the Kent State student, not the bluegrass singer. Thats too bad, I'm a fan of the second one, but not the first.
I don't think I could really choose between the two, but I would love to have dinner with MSG Gary Gordon and SFC Randall Shughart.