Shadowrun: Null Value
Shoot straight, conserve ammo - shadowrunners often think about threats in terms of guns and bullets. That's thinking too small. Why shoot someone when you can drain their entire bank account without coming anywhere near them? Or you can burn whatever ID they're using, forcing them to restrict their movements and travel. Or you can broadcast their current location to all their enemies, so that a bullet still find them, but you don't have to fire it.
All this and more can happen in the Matrix. From hacker and technomancer groups to rogue AIs to mysterious entities, the Matrix is full of threats that shadowrunners need to know about. This book lists ten of them that can fuel campaigns, character development, and more in any Shadowrun game.