Aah this is hard, there's so many actors I like, but Arnold Schwarzenegger is probably my all time favourite, I mean yeah he's not an amazing actor yaddayadda but I just seem to enjoy the characters he plays, and sometimes the rough acting can really have comedic value. I suppose he brings a lot of his own personality into whoever he plays. Otherwise I might would have been a four-way between Leonardo DiCaprio, Robert De Niro, Johnny Depp all pretty much put on a great performance in every role they play, and Clint Eastwood because he's a badass motherfucker.
I couldn't make my mind up on female actors, maybe Winona Ryder, Uma Thurman, Natalie Portman?
All really good choices there Junco. Natalie Portman would have to be my second choice as well.