I'll start with the obvious, Sandwich [1] by xkcd [2]:

Yes, this question is a copy of What’s your favorite “programmer” cartoon? [3] but where's the harm in a Super User equivalent of such a popular question?
ACCEPTED]
Just added today but I think this will be a classic XKCD:

Title Text: They could say "the connection is probably lost," but it's more fun to do naive time-averaging to give you hope that if you wait around for 1,163 hours, it will finally finish.

I know we have quite an XKCD inflation here, but I have to post this one, since it's my definte all-time second-to-none never-gonna-find-a-better-one favorite:
It's simply so true.


puts instead of printf, or included \n last in the string! - gustafc
Another xkcd (I know, what a cliché!)
Title text: "When I look into your eyes, I see JPEG artifacts. I can tell by the pixels that we're wrong for each other."

My alltime favorite:


This is the best ever XD




ERR of course! Not to mention the amusement over the Boston police overacting and calling in the bomb squad.
http://laughingsquid.com/aqua-teen-hunger-force-promo-causes-panic-in-boston/
