Ha, a bunch of my favourites have been nominated - but I'm still having trouble limiting it to ten. Some of these might be repeats - I didn't read too closely.

Book Series:
Tamora Pierce's Tortall books (especially the Protector of the Small quartet)
Simon R. Green's Hawk and Fisher books (two short story collections + two novels)
Tanya Huff's Keeper Chronicles
David Weber's War God's Own series
Mercedes Lackey's Bedlam's Bard series

Books:
Neal Stephenson's Snow Crash
Cory Doctorow's Little Brother
China Mieville's Un Lun Dun

Western Comics:
Warren Ellis' The Authority
Bill Willingham's Fables