At conventions, of all the Star Trek actors, which one's do you find most entertaining?
I personally think it is Brent Spiner.
Interesting, since I've encountered Brent Spiner a couple of times in the real world, and my experiences with him have been "eh," at best. Maybe appearing at a convention he's better.
But to answer your question, I'll limit it to some I've actually met, rather than just seen on stage.
Jonathan Frakes was awesome. Friendly, and approachable. And really nice to my daughter, which scores points.
Marina Sirtis, wonderful and funny, and damn sexy, too.
LeVar Burton, soft spoken, but kind. Seemed genuinely concerned when I mentioned that I had a heart attack on his birthday.
Walter Keonig, quiet and soft spoken, but approachable.
John Billingly was nice and warm. A pleasure to speak to.
Conner Trineer was funny. Laughed at my joke about how God made children cute for a reason. (this was in response to his own stories about fatherhood.)
Armin Shimmerman was unbelievably kind and gracious. His line went so slow because he spent time with everyone.
Cirroc Lofton was nice and down to earth.
George Takai was just loving life and having a blast.
Nichelle Nichols was kind and warm, but at times a bit distant. I guess everyone has their days.
Wil Wheaton was surprisingly nice and humble. Good sense of humor.
Majel Barret always made herself accessible to the fans. A very down to earth person.
Gates McFadden I could do without. Very cold and unapproachable. Just wanted to go through the line and get done with it. Not very gracious with the audience.