RPG a Day 11 Favorite RPG writer:

The toughest question so far, there are so many great writers over the years.  Gary Gygax , Dave Arneson, David Cook, Tom Moldvay, Frank Mentzer, Tracy and Laura Hickman, Mark Acres, Lawrence Schick, Jim Ward, Joseph Goodman, Jon Mar, Harley Stroh, Greg Gillespie, Michael Curtis, Jobe Bittman, Daniel J Bishop, Zach Glazar, Stephen Newton, Mark Bishop....the list goes on.
There are plenty more writers that I just can not recall at the moment, and this list is only of D&D and DCC RPG authors!  There are even more writers for other games.

By far the most prolific in his time was Gary Gygax.  He left a lot up to the DM in running his adventures, but the bare bones were there to make the adventures fun and exciting.  He was great, but there were a large number of even better writers that wrote for his company, and the many other companies that formed afterwards, that were almost as influential on gaming.

I honestly can not say that I have a favorite writer, or even a group of writers.  Every one of the above listed writers has a unique style of writing.  All of them create material to inspire your own campaigns and adventures.  Ultimately, it comes down to what you find useful for your table.

I guess you might say that my "favorite writer" is you, because it is what you take from the past and current writing to create for your own gaming groups that matters.  Loot, plunder, and outright steal if you have to, for material to keep your friends having fun around the table.  You never know it may turn into a marketable adventure or campaign setting some day, that will inspire some other gamer's table.