UXM 1-9, and, the tenth is a much more difficult choice, but I'll say X-Men 6.

Weeding out UXM, because it's so head and shoulders above the rest, to give other titles a chance:

X-Men 6
Ms Marvel 1
Luke Cage 1
Avengers Kree/Skrull War
Champions
Fantastic Four 5-7
Hulk 7-8

Samy wants to see the following collected editions:
X-MEN: CLAREMONT/JRJR OMNIBUS, X-FORCE OMNIBUS VOL. 2, 
NEW MUTANTS OMNIBUS VOLS. 1-2, GENERATION X OMNIBUS
PUNISHER (1987) #1-18 OHC,
PUNISHER WAR JOURNAL (1988) #1-24 OHC,
X-MEN: REVOLUTION OHC
X-TREME X-MEN VOLS. 1-2 OMNIBUS, WOLVERINE: HAMA/SILVESTRI OMNIBUS,
LEGION ARCHIVES VOL. 14, KNIGHTFALL OMNIBUS
LEGION OF SUPER-HEROES: EYE FOR AN EYE DELUXE HC