Stephen Donaldson: Thomas Covenant series (CLASSIC CLASSIC CLASSIC with MANY moving and heart-wrenching sequences). For me this series is second ONLY to the LOTR.
When I saw this thread, I was planning to mention the Covenant series as well. But someone beat me to it 
It's second on my list as well, after Lord of the Rings. The OP described it, after reading the first book, as:
This is a story about an incredibly depressed, pessimistic loser who has to carry a mysterious "magic gold ring" to the "council of Elrond Lords", led by a "ranger" girl because the "Dark Lord" is going to return to conquer the world. This is another Lord of the Rings clone, except this time, the hero has leprosy, is a rapist, and a moron.
It's exactly what made the book stand out for me. Not the LoTR clone part. Which I don't agree with really. Most books can be viewed as LoTR clones, where the ring is replaced by some other artifact or a piece of knowledge and the 'Dark Lord' is replaced by some other antagonist(s). What I did like was the fact that the 'hero' in this series is flawed, and goes through a massive personality change throughout the series, instead of being the 'I can do and know everything and I reveal more and more superpowers and superknowledge with each passing chapter' type of hero that you see all too often. These type of heroes annoy me to death.
Someone else mentioned Terry Pratchet, the Discworld series. If you like a lot of humour in your fantasy, this is the one to read.
If you like something more 'out there', I would recommend 'Perdido Street Station' by China Mieville. It's a mix of fantasy, horror and SF, steam punk like, set in a rather grim city 'somewhere in time'.
Even more out there is the Gormenghast trilogy by Mervyn Peake. The book has one of the baddest villains I have ever seen in any book, a character called Steerpike. I have to warn though. This one is for language lovers. People who like to read for the sake of reading and who enjoy language. There's little action. The author, Mervyn Peake, is a painter first by profession and he also wrote books. His painting background shows in his books. He writes like a painter. What I mean by that: he uses words on paper to paint a world, an image and atmosphere, and the characters in it, much like he would use paint on a canvas. His books are very detailed and he uses a very broad vocabulary. The actual action is thin.
