To answer the question, I can't say as though I have favourite actors. However I have some favourite performances....
Robert DeNiro in Taxi Driver - I think these days he has completely lost what he had and is always just DeNiro but in Taxi Driver he truly brings Travis Bickle to life in a more real way than I think any character ever has on screen. To me, that is the #1 performance of all time. I also think it was Harvey Keitel's best ever role, as Sport. For a 14 year old actress too, Jodie Foster was amazing too... and even Scorcese himself in his cameo role as the passenger who tells Travis to pull over and look at his wife having an affair with a "my pals" through a window and tells him how he's gonna kill them both and what his gun can do to a woman's pussy is just excellent, the way he says "What do you think about that?" after it is unforgettable. My #1 film ever.
Griffin Dunne in After Hours - another Scorcese film (and his hidden gem in my opinion, his best along with Taxi Driver). This unknown actor has such a great performance as Paul Hackett, the ultimate boring office-job guy with no life, who gets himself stuck in a wild night he just wants to escape. All he wants to do is get home, and the film captures so well that feeling everyone has had at times where they just wanna leave wherever they are and go home (the whole film is about that) and Griffin Dunne's performance is a big part of that. One of my top 5 films of all time - unbelievable. Scorcese's hidden gem. Forget Goodfellas & Casino, and Raging Bull & Mean Streets, and New York New York & King Of Comedy, as great as they are.... this film is easily his best along with Taxi Driver if you ask me.
Eddie Murphy in Coming To America & Beverly Hills Cop - Eddie showed he was the king of comedy at the time in these 2 films. Moreso in Coming To America, playing multiple characters too, he is at his funniest ever. And in Beverly Hills Cop he really does make Axel one of the best & most memorable film characters ever. Can you imagine if Stallone played him like he was meant to? It would have sucked. I'm not a Stallone fan at all.
Everybody almost in The Texas Chainsaw Massacre (original) - strange choice I know, but fucking hell that cast is amazing. The most realistic performances I've ever seen in a horror film BY FAR. Probably much due to the conditions the film was made in if you read the stories about what Tobe Hooper put his actors through...