For me, I have a few but these 2 are the ones I enjoy the most:
Gregory Fremont-Barnes: Most of his books were published by Osprey and as such are short, however they are well written and provide some good insight into the topics he writes on. His account of the Battle of the Nile in 1798 is one of the best I have read so far and his book on the Royal Navy from 1793 to 1815, covering the organisation, structure, ship types etc. of the navy in the period is both a good overview and a great reference book.
Gareth Glover: His books are nothing special and as a writer he is all over the place for me, sometimes describing the subject he writes on with good accuracy and detail in a readable manner, sometimes his writing can be confusing with errors in both fact and interpretation. However the reason why I consider him exceptional is because of his work as an editor and publisher of primary sources on the Napoleonic Wars such as diaries of soldiers, official documents etc. which provide some pretty important material on the period.
Who is your favourite historian(s)? By historian I mean someone who writes books examining history, makes documentaries or contributes to the study of history in any other way. Both dead and living historians count.
My favourite popular historian and my favourite historian overall is Barbara W. Tuchman, because she's the best historian I ever read when it comes to mastering the art of writing.
My favourite biographer is M. J. Carter, for The Three Emperors: Three cousins, Three Empires and the Road to World War One, which is surprisingly excellent. It's a broad subject and I never heard of her when I decided to read it, but she handled it splendidly.
My favourite military historian is Sir Antony Beevor (Stalingrad and The Downfall 1945 are vivid, well structured and I like the attention he paid to the ordinary lives of people).
My favourite cultural historian, Romanian historian and my most read historian (20 books) is Lucian Boia. He mostly deals with the history of ideas and the imaginary. History and myth in Romanian consciousness (1997) was huge in redefining the way people see Romanian history. He also writes books that are basically extended essays on various historical subjects. I never know if I'm going to agree with him when I read one of those, it's 50-50. He's easy to read and has an adequate amount of witty humour.
My favourite history podcaster is Mike Duncan. His podcasts are easy to listen to while enjoying a walk.
My favourite natural history documentary maker is Sir David Attenborough, for his voice, attention to details, the soundtracks and the amazing visuals.
My favourite history documentary maker is Bettany Hughes. She makes everything interesting (even when there's a subject I don't usually care about, I know I'm going to like the documentary) and finds unique ways of looking at things from the past.
I have favourites for other categories, but I don't like them that much overall in order to mention them. It's fun to start sentences with "my favourite" multiple times in a row, it reminds me of my childhood, when I didn't realise how annoying repetition is how annoying repetition is.