Volume 1, Issue 11 hands down:
But this picture doesn't do it justice. I feel it is best viewed with the back and front cover as a whole. This is deffinitely in my top 10 issues as well (Possibly #1).
And despite the fact that Farley's turtles creep me out a little, City of War Part 8 is a close second:
ETA: cowabunga14! When I scrolled up and saw issue #11 twice I thought I had accidentally double posted somehow, LoL.