Adding my vote for both Martin & Hobb, both are disturbingly enthralling.

How about the Night Angel trilogy, by Brent Weeks? It's got magic & assassins.
http://www.amazon.co.uk/Night-Angel-Trilogy-Brent-Weeks/dp/0316085146

The Rogue Agent series by K E Mills (aka Karen Miller) is a WIP, if he doesn't mind. She's got 3 books out already:
http://www.amazon.co.uk/Accidental-Sorcerer-Rogue-Agent-ebook/dp/B00550N96M/ref=sr_tc_2_3?ie=UTF8&qid=1326366117&sr=1-2-ent