Mine would be THE BRAVE AND THE BOLD comic book; especially the Jim Aparo run… Those years, (early 70s to early 80s) were the best comic reading days of my life…And seeing Batman teaming up with other heroes, like Dr. Fate, Phantom Stranger and Green Lantern was a hightlight!
Batman: War on Crime is one of my favorites
The Killing Joke 
Jim Aparo is amazing. I think it was his rendition of Batman I first saw when getting into comics. Beautiful stuff.
I don’t have an all time favorite Batman series but my current favorite Batman ongoing is Detective Comics.