(All fantasy series btw)
The Sword of Truth series by Terry Goodkind. It's pretty long so it'll keep you going for a while.
Pretty dark and gretty, with plenty of mature material.
Also Brent Weeks, The Night Angel Trilogy.
Like Sword of Truth, quite dark and gretty, and gets pretty graphic at times.
A classic is The Wheel of Time series by Robert Jordan. Not as dark as the others, but plenty of pretty extreme action.
True fans will probably be afronted by this, but I consider this the Dragonball Z of fantasy books just for the share amount of over the top action in it.
