Ever met a GM?
I met Karpov in Mexico, he signed me a book. I've played against Judit Polgar in Mexico too in a simul when she was a teenager. She came with her sisters. In the World Chess Championship 2007 in Mexico I met Anand, Kramnik, Svidler, Moresevich, Leko, Gelfand, Aronian, and Grischuk. Great Tournament for Anand...

As a member of the Allentown, PA chess club, I had the privilege of playing a GM (sadly, I cannot remember his name) in a simul a number of years ago. He soundly defeated us all (including 2 masters), except one member who got a draw. Dave (USCF 1700) was our hero for the next several weeks.
I also got to meet and talk with Gennady Segalchik (sp?) at East Stroudsburg University when he was playing in the PA championship. He was not yet a GM, but at 2600 at that time, he was soon to break the barrier.
Finally, at the World Open, I rode in an elevator with Patrick Wolff and asked GM Dzindi . . . a question. I had been seeing signs all over the tournament hall in Russian, and I finally asked this famous GM what they meant. He replied, "No smoking."
Thus endeth my GM encounters.
I arm wrestled GM Benko once. We had one of those brief GM draws.
I assure you this is true. It was one of Kopec's camp many years ago. I believe that I played Nakamura and his brother at the same camp and took a beating. I don't have the score sheets to verify my memory. I found my game with the brother quite interesting. I had beaten tactically by a very young player on quite a few occasions. However, this was the first and only time someone so young had so completely tied me in positional knots. I wish I had that game score.

In my chess carear I played:
Lothar Vogt
Alexey Suetin
Nikola Padevsky
Kevin Spraggett
Oleg Korneev
Carlos Matamoros
the first three in "simul" Draw whit Vogt e Suetin
The others in Portuguese Chess League Championship. The results? 0-0-0, but not smashed ! Two... Well they got me in the transition to middegame but I resist till the ending, With Kevin I lost in the ending. Whit Matamoros he make a theoric novelty in 18 move of a Fiacheto King's Indian, and I passed 50 m to reply, and... time trouble! With Korneev I got a splendid position on the black side of a Spanish game, Bird Variaton, but by 30 move a tricky move of Oleg caught me like a litlle "bird".
Well the sensation? No fear! They are not superplayers! Well, a 2000 Elo could play with a 2500-2600 GM and if he knows Opening Theory can resist. In all this games I don't see "genius" or a super view of the secrets of the chessboard. Experience, and capacity of guess the rirgt moment to take some sensible advantage, yes! But no glimpses of crushing me with tactical sharpness or analysis capability "other world" !
Whit Spraggett, me with W 1.d4 - f5 2. e4 -fe4 3. Nc3 he played 3...b6 the old Tartakower move, and I playd simple, and got a equal and sound position till 27 move.
One point: Never siiting front a GM with the idea: The man will crush me! Never! Other point...without some teoretical preparation, well ...you will be trounced in the Opening, no doubt! With my games with Oleg Korneev and Spragget, I spent almost 4 hours in the preparation of the Black side of Bird, and the Staunton Gambit of the White side of the Dutch.

I've met a GM, but never played one. He talked about the queen's pawn opening and the double bishop sacrifice against the kingside castled king. I never used that knowledge, though. I always play the queen's gambit.

I met a GM in Washington Square Park some time ago. He wanted to charge me $30 to play a game with him and I respectfully declined since I was broke at the time. Then he mentioned that he wanted to go to the Manhattan Chess Club, I told him to take the 6th Avenue bus but he apparently felt he was too good to take a bus like us commoners. I had to leave so I bid him adieu. I didn't catch his name.

I've met many, but the only ones I ever felt nervous about was meeting Karpov in Las Vegas last summer and Kasparov in Slovenia last November. Oh, my mom reminded me recently that when I was in 2nd grade, I played now-IM Naroditsky in a simul and when she tried to take a picture of me and Naroditsky, I ran and hid under a desk. Of course Naroditsky himself was a 7th grader at that time. There's no doubt IM Naroditsky will become GM Naroditsky in the very near future.
My first GM I played with in a real rated OTB game was against GM Matamoros a few months ago. Everything that I had seen published looked like he was going to go King's Indian. So what happened? He plays a English Defense against me. So much for preparation.
that reminds me! my brother went to the wycc, and saw kasparov!

The only GM I have had multiple conversations with is Rossolimo back in '74 just before he died. I've exchanged a couple of words with Anand (just before the start of game 10 in the WCC match with Kaspy), Larsen, Najdorf, and Christiansen. The Najdorf meeting was just after game 9 of the Kaspy-Anand match. When Najdorf said, "I must tell Garry to take better care of my variation," I almost asked him who are you to think that the Najdorf variation is named after you! I was able to catch myself before committing one of the biggest blunders of my career.

I met Gregory Kaidanov once at a lecture, but the GM I know best and have met several times is Varuzhan Akobian. I've been to several lectures with him as he visits Chicago quite often. I run the chess club at my son's school and Akobian has stopped by his school a few times. As it happens I saw him yesterday and will again today as my son is taking his first private lesson with him today.
I also know a couple IMs, NMs, and one FM, but I'm not sure that counts.