Most of my favorite actors and directors are dead.
My fave directors among those currently active include the Coens, Tarantino and Cronenberg. My fave actors currently active include Robert Duvall, Johnny Depp, John Malkovich and Christian Bale. Of these, I think the only combination that have actually worked together are Malkovich and the Coens (Burn After Reading).
The Coens tend to work with the same pool of actors for the most part, but Depp and Bale starring opposite each other (possibly with Depp as the villain?) in a Cronenberg thriller could be awesome. Malkovich with a key but quirky role in a Tarantino film (not unlike Christopher Walken's one scene cameo in Pulp Fiction) would be pretty cool too.