I collect autographs - only Star Wars unmodified Original Trilogy and including both cast and crew.
So far I have got 29 different signatures spread out on two posters, all acquired in person of course, all at conventions. Carrie Fisher’s the only “big” actor though, and Ben Burrt’s the only “big” crew so far.

I have lost count on how many times I have crossed paths with Dave Prowse, Kenny Baker and Jeremy Bulloch at conventions. You see them often: signing autographs for money seems to be their only livelihood. They are very nice guys.
I’ve also seen Anthony Daniels five times - signing table and backstage: He has a bit of a bad reputation but I have not had any bad experiences with him myself.

I have actually met Don Bies twice (not at cons) but never asked for his autograph as he is only posing in Fett’s armour in the SE and was crew in the PT.
I have also met Ray Park (Darth Maul) a couple of times. Back when I started going to cons, I did get Andy Serkis’s signature but he does not count for me, because I see the TFA as an abomination.