Quentin Tarantino is arguably one of the most gifted filmmakers on the planet and has made many movies in his time. In many of the movies which Quentin has made, you can catch either Samuel L Jackson or Christoph Waltz or even both. Quentin has now admitted that he just finds himself writing roles for the two actors.

Christoph Waltz in Inglorious Basterds
Tarantino explained, "It's hard not to write for these guys; they say my dialogue so well. For 10 years, I'd write something cool; Bill, for instance. For seven months of the year and a half I spent writing 'Kill Bill,' Bill sounded just like Sam."
Quentin continued, adding, "The way I write, I always kind of fancy it as poetry, and they're the ones that make it poetry; they come out of my pen. Sometimes it's not even appropriate, but I can't shut it off."

Samuel L Jackson in Pulp Fiction
Samuel L Jackson has appeared in a number of Quentin Tarantino movies, including Pulp Fiction and Jackie Brown, which Christoph Waltz starred in Inglorious Basterds, while they both appeared together in the latest Quentin Tarantino movie Django Unchained.
It will be interesting to see if Samuel L Jackson and Christoph Waltz have a role in the next Quentin Tarantino movie.
Django Unchained movie trailer