This troper firmly believes that anyone who doesn't wish they could do this is either not human or a liar.
This one as seen below, which is a crowning moment for anyone with many female friends who actively engage in the use of the internet and sees the crap they put up with.
Who turned out to be unexpectedly good at geography, derailing our attempt to illustrate their country's attitude toward the rest of the world
#734, #735, and #736. All three are among the best strips Munroe has done, and even garnered praise from xkcd's primary hateblog. And all three appeared in the span of one week.
For Randall for strip #687: the math checks out to be within the error bars of the equation given.
It's a bird... it's a plane... it's Sagan-Man! On a serious note, eliminating crime and improving scientific research at the same time would be very awesome.
In the same stream of thought, while not part of the main comic, the now famous radiation chart◊ is a fairly awesome moment for Randall.
Umwelt. The image changes depending on what browser you are using, what OS you are running, how wide your screen is, the height of your screen, where you are coming from, and your geographical location. Known variants include (but are not limited to): Wikipedia, Reddit, the UK, Alaska, Florida, Illinois, Germany, the Google corporate network, MIT, a mobile browser, the Chrome browser, Netscape Navigator, Israel, the Armed Forces, and many, many more.
Every Major's Terrible, which bemoans the uselessness of liberal arts degrees while pointing out how the various science majors have their own deficiencies... all to the tune of "Modern Major General". Almost immediately, Youtube videos started popping up of people attempting to sing the damn thing.