My favorite single comic book panel of the year is a sentimental choice. It's one that almost made me cry, from All-Star Superman #10 (May 2008), written by Grant Morrison and drawn by Frank Quitely and Jamie Grant (click to enlarge on all the pictures below):
This panel appears near the climax of both issue #10 and the series as a whole. (I need to describe both, so spoilers ahead, though I suspect that most TB readers have read All-Star Superman.) The 12-issue span of All-Star Superman is a prolonged epitaph for the Man of Steel; the first issue opens with Lex Luthor luring Superman into a trap that poisons his cells and slowly kills him. By issue #10, titled "Neverending," Superman, almost dead, has begun to dictate his "last will and testament." In straightening out his affairs, he searches for a definitive answer to the plight of the Kandorians, a population of Kryptonians who survived the explosion of Superman's planet only because they were shrunk to microscopic size, squeezed into a bottle, and kidnapped by the intergalactic villain Brainiac. Superman's friend Leo Quintum, a Morrison/Quitely creation that combines Einstein's brilliance with a dandified fashion sense, makes a bold suggestion to the Kandorians: just live as creatures "smaller than germs" among us humans. After much debate, Quintum's suggestion is accepted, and the Kandorians break their bottle open and settle on Mars.