Dunkelzahn’s Will. The entire book is a cross between a Awesome and Funny, with the more you know of the setting, the funnier it becomes. Some examples:
Giving a powerful Macguffin to the government of either Tir Tairgire or Tir na nOg, whichever first gives the full biographies of all their government officials. Given that both nations are run by immortal elves…
The Spirithiel quote at the end of that bequest reads, more or less, "Shouldn't knowledge be available for all? Share the language."
“To Alamais [another Great Dragon], I leave the fruitcake we have exchanged every Christmas since 2020. Unlike you, I’m really dead.”
Leaving $10 million so a band can complete a rock opera.
His one foray into free-form sculpture, now in various museums and called “Pre-Bronze Age Cave Reliefs 1-12,” after he smashed it.
“For a period of ten days beginning on 14 February 2057, Lars J Matthews will cease to posses any legal status. He will be stripped of all evidence of legal existence, including SIN, credsticks, Doc Wagon contract, bank accounts, and so on. To the individual or group who ends Lars J. Matthews’ physical existence during those ten days, I leave all of Matthews’ assets and 1 million nuyen for a job well done. If Mr. Matthews survives and can prove his identity, his legal status and all possessions will be restored to him. Haven’t you heard? Never deal with a dragon, Lars."
“To the owner of the sky-blue Chrysler-Nissan Jackrabbit that was crushed by a falling chunk of plascrete on October 26, 2045, I leave my 1964-1/2 candy-apple red Ford Mustang convertible. Sorry for the inconvenience – I had an itch that I couldn’t reach and caught the corner of the building with my claw."
The entire Safehouse supplement. From the beginning with Kane having to sneak into Comic Con dressed as a Stormtrooper, to /dev/grrl given homework to tag 100 transit buses, to all the Shout Outs, to one of the sample safehouses with you staying with an elderly Troll grandmother that keeps talking about her grandkids, to the the image of the tagged bus with "HOMEWORK'S DONE! HAPPY?" in big angry letters.
In the 5th edition rulebook, when introducing magic, it comments that when something new is introduced to the world, two questions are asked. 'How can I make money off of it', and 'how can I use it in porn'?
Shadowrun itself could be compared, in terms of player attrition, to Paranoia and Call of Cthulhu. Therefore, as has been alluded to in many, many manuals and documents, when a mission goes unexpectedly right, the player characters start getting edgy, waiting for another shoe to drop. An experienced GM can quite happily leave that shoe dangling for several more sessions, until the players start checking their soy for intricate toxins and their boots for large boxes that read 'Point towards enemy'.