Interesting question - very difficult to answer since only one choice is allowed but I'll go with Nimzovitch.
CalbaMan's Question

capablanca is my choice, his posture on defense and offense is meaningful to me.i also want him to be my coach in positional play if he were alive today.

I wouldn't mind sitting down and having a chat with Emanuel Lasker. He managed to make a couple non-chess-y contributions to the world that seem pretty interesting to me. Some chess players like the illusion that chess automatically makes them an intellectual, but this guy actually was.

Morphy...If he was the unofficial world champion, he was probably an unofficial Grandmaster.
I'd smack Fischer upside the head for that remark about chess being like a can of chili. No one understands it. It makes no sense.
I'd also ask him about the Jewish thing. He'd probably be reasonable and change his mind.

I wouldn't want to meet dead grandmasters. That would be uncomfortable. But, I wouldn't mind having tea with Anand and his wife. They seem nice
If you could meet any grandmaster [dead or alive] who would it be, and why? In my opinion, I would definitely want to meet Bobby Fischer.
That's just my choice. Give me your opinions!
~ CalbaMan