Darkness by Boulet is probably the best 24-hour comic ever made. The writing and art are just too good to be true and even in its current imperfect translation (the comic was originally in French) it has some classic lines in it.
Speaking of which, the other day I read Daniel Davies' The Christmas Sermon for the second time, a year after I'd first read it. Back then, I went as far as to read it aloud to Aggie. It's still hilarious a year later.