I'm trying to put together a definitive list of Adam Hughes covers. This is what I have so far. Please feel free to add anything that I may have missed.
Beautiful Killer #1
Buffy the Vampire Slayer Season 8 #30
Catwoman #44-83
Chassis (Hurricane) #1
Chassis (Millenium) #1
Classic Star Wars A New Hope #2
Classic Star Wars Return of the Jedi #1
Comics Greatest World: Ghost
Danger Girl #3 (VAR)
DC Comics Presents Batman (2004) #1
DC Comics Presents Superman (2004) #1
Detective Comics #858 (VAR)
Dirty Pair Run from the Future #1 (VAR)
Elementals #12, 17
G.I. JOE (IDW) #2 (VAR)
Gen 13 Ordinary Heroes #1-2
Ghost (1st series) #1-3, 5-7
Ghost Special #1
Hammer of the Gods #3
JISL creating Aquaman #1
JISL creating Batman #1
JISL creating Catwoman #1
JISL creating Flash #1
JISL creating Green Lantern #1
JISL creating JLA #1
JSA Classified #1, 2 (VAR)
Justice League America #31-52
Justice League of America (2nd Series) #6 (VAR)
Justice League Quarterly #1
Lady Rawhide Special Edition #1
Legends of the Stargazers #1-6
Legion of Superheroes (2nd Series) Annual #1
The Legion #35 (VAR)
Legionnaires #7, 13, 14, 16, 50
Liberty Meadows #20
Marvel Swimsuit Issue #2
Maze Agency #1-10, 12, 13, 19
Mister Miracle (2nd series) #19
Pain Killer Jane (Dynamite) #1 (VAR)
Penthouse Comix #2
Power Girl #1, 2 (VAR)
Red Sonja (Dynamite) #2 (VARM 7, 8
Rose and Thorn #1-6
Sensational She-Hulk #52
Serenity Better Days #1-3
Spoof Comics Presents #1-7
Star Trek The Modala Imperative #1-4
Star Trek TNG The Modala Imperative #1-4
Star Wars Boba Fett Overkil #1
Star Wars Legacy 1/2, 1-7
Superman Returns Prequel #1-4
Tomb Raider #18, 32, 33, 34, 41-50
Tomb Raider Gallery #1
Tomb Raider Jounreys #1-4
Valor #8-10, 12
Vampirella #1-3
Vampirella Lives #2
Vengeance of Vampirela #6, 7, 10
Voodoo #2-4
WildCATS / X-Men The Modern Age #1
Wildstorm Summer Special #1
Witchblade #87
Wonder Woman #139-146, 150-161, 164-174, 176-178, 184-197, 600 (VAR)
X-Men Classic #71-79
X-Men The Early Years #3, 12, 15
Xena Warrior Princess The Orpheus Trilogy #1 (VAR)
Zatanna #11-
Zorro #3