Marco, I'll be mailing you soon...........
Anyways:
Alan Moore - everything, he never fails
Grant Morrison - Invisibles is a must and Doom Patrol and Arkham Asylum are very good too. Animal Man and Filth are worth taking a look at as well, although the "meta-comic" stuff in them can be a bit hard to digest (at least for me it is)
Garth Ennis - I'll second Preacher that Tisbor mentioned and add The Boys and Punisher. Haven't checked out his war comics yet but will do.
Warren Ellis - first half of Transmetropolitan series is pure genius, but then it starts to repeat itself too much, I think. Also see City Of Silence and Desolation Jones
Ahh, there's so much good stuff... The Walking Dead, DMZ, Fables, The Goon, Hellblazer, Greek Street, Hellboy and its spinoffs.... and Fletcher Hanks!!!