Shadowrun/YMMV


 * Game Breaker/Elite Tweak: Third Edition has an Edge called "Connected" that, when taken for a vendor contact, allows you to buy from that contact at the list price or sell at the street price, which can be as much as three times more. Thus, taking that edge for two contacts (one to buy from, one to sell to) allows a player to get ridiculous amounts of money while the GM isn't paying attention.
 * The physical adept can become noticably broken if you use initiation to offset the Essence cost of cyberware.
 * The chemical DMSO. If you splash it on someone, it allows for other chemicals to be absorbed into the DMSO-coated skin. Additionally, armor has little to no effect, so if someone hits you you with it, you WILL be affected. The end result being that if you mix DMSO with poisonous drugs and load it into a squirt gun, you get a super soaker that deals one-hit kills. You can hear details about how this can affect a game environment in this video.
 * Germans Love Shadowrun
 * High Octane Nightmare Fuel: Cyberzombies, which are metahumans implanted with so much cybernetics that they effectively die. Their souls are then forcefully tethered to their bodies through magic and technology. Few last longer than a year before cancer and necrosis rots their bodies away, and most of them aren't what you'd call sane. Oh, and all of this is done completely against their wills by corps who want a temporary asset.
 * Chicago, which ended up suffering an outbreak of nasty insect spirits. Much of the city was blown to hell trying to get rid of them, and what remained was quarantined by the UCAS military, leaving everyone still there to fend for themselves. And that was the good ending of this saga.
 * As an In-Joke, the nuke that was used in Chicago was centered at the location of FASA's headquarters.
 * Bunraku parlors: Yakuza agents acquire pretty girls, either by abducting them personally or through the international slave trade, and have black market surgeons install cyberware that allows the Yakuza to replace their personality with a digital chip. As far as the customers are concerned the girls are perfectly happy to be there. If the girls are lucky, the chip suppresses their mind to the point of unconsciousness; otherwise...
 * And then there's the Horrors...
 * They Just Didn't Care: prebuilt characters from the 4th Edition corebook. There is something wrong with every one of them. Barely any have a Fake SIN (basically an ID card required in all civilized areas), and that's just the beginning. The Technomancer? Gets -1 dice to Reaction and Agility tests because of being encumbered by worn armor (the "maximum armor" rule is stated in the same book, no less). Same goes for the Weapons Specialist from the More Dakka entry. She also doesn't have anything that would allow her to use that laundry list of guns more than once per turn (as opposed to other combat-oriented premades like the Street Samurai and the Gunslinger Adept). Drone Rigger? Has cybernetic eyes (with Image Link modification built in by default) and goggles with Image Link as the only modification. Even with no Min-Maxing, a player with experience in Point Build Systems would achieve better results.