Part two of my fantasy overview.
Regardless of the label, this is a definite "brand" in the fantasy genre. Characters are shades of grey and their motives are less than heroic, the outlook is more cynical, things do not end happily ever after. The settings tend to have no non-human races and lower levels of magic. Whereas some fantasy is conservative, the gritty variety is more likely to include explicit language/sex/violence. You probably already know whether you're interested, but consider the following authors.
George RR Martin
One of fantasy's big names. His novel A Game of Thrones made an impact (with its political focus and character deaths) that changed the genre. The first three books combine a continent-wide story and a swift pace that were widely acclaimed. The next two books have been slow in coming and opinions vary, but the influence of this series should not be underestimated, especially since it spawned one of the first successful epic fantasy television series.
An older writer who occupies a unique niche in the fantasy genre. Cook's novels are very military in nature, focused on soldiers in a grim fantasy world. The magic is actually both dramatic and creative, but it is held only by powerful sorcerers who are separated from the soldiers on the ground. His books generally read very well on their own.
A newer entry in the subgenre, beginning with The Blade Itself trilogy and following with standalone novels in the same world. Strong pacing and a variety of characters that isn't seen in many series. This is combined with perhaps the most cynical perspective on this list, which will repel or attract different kinds of people, but there's a strong thoughtful undercurrent to his work.
Not quite the same as some of the other authors on this list, Lynch's Lies of Locke Lemora series is fantasy heist story. It has sharp dialogue and clever plots. Overall his world is relatively low magic, and in addition to the main characters being thieves he includes the bloody consequences of their actions.
Another arguable placement, since Gemmell generally writes epic fantasy with a dark edge. His stories almost always resolve in one book (both a strength and a weakness) and include a variety of tropes that are taken in directions you wouldn't necessarily expect.