Well, I have no overall favorite as that's as impossible as picking a favorite movie, but I do have my list of favorites.
In no particular order:
Tommy Lee Jones - I just like his 'commanding' presence in movies. His voice is also a big plus. He's been in great movies such as The Fugitive, Under Siege, MIB, and US Marshals.
Kurt Russel - Great actor. Tombstone is one of my favorite movies, Wyatt Earp being my favorite Western tale, and I like many other of his movies such as 3000 Miles Till Graceland and Escape From L.A.
Kevin Costner - I just like Costner. I think all of his movies are good. Even the "fabled" bad ones such as Waterworld. He plays one of the most bad ass characters in any movie, 3000 Miles Till Graceland. Robin Hood was also great.
Steven Seagal - Oh yeah. Everyone hates him. I love him. Under Siege is my favorite action movie by a long shot. I like all of Seagal's movies just because of the way he is - some cold, one-toned, untouchable tough guy who slaps everyone around. His voice is hilarious and in his prime, was a very good martial artist, especially in Aikido.
I also like Arnold due to his 80's action movies, Stallone for various films, Johnny Depp, and Gary Busey.
As for my favorite actresses ... who knows. I would have to sit and think about it. I don't feel like doing that right now.