Okay, I know it's way early, but I've already got two strong nominations for today.
Second is this thread, starting about halfway down (I can only ever find mid-thread comment links through trial and error, and so far, it's been all error) when DrillPress and x84jdh start speculating about the types of slash-fic adventures that Lt. Reginald Barclay might embark on.
Both of these posts made my computer very lucky that I wasn't drinking anything at the time, if you know what I mean, and if not, allow me to demonstrate:
So, can anyone compete with those? More importantly, who's got spit-take gifs they want to share?