So, some things I've done in the recent past.
In my nWoD campaign, the PCs encountered a cauldron. One of the PCs saw something etched on the inside, and ran their finger along it to brush away the dust. The writing on the inside cut their finger, and started to glow, so she ran her bloodied finger across them to feed it more. The runes lit up, and the cauldron filled with blood of its own accord. The caretaker of the shop fell over dead, and was taken away in an ambulance... leaving the PCs wondering what happened. The cemetery in the back (this being a church attached to the shop of antiquities) started to see some activity, and when the PCs investigated, they were attacked by zombies. (the 'twitch' kind which are quick. Infectious by bite, regenerating, feral type)
The PCs dealt with the zombies, then realized the dead guy's probably one too. They sent a friend to go deal with it, while they tried to determine what to do with the cauldron. They finally figured out what it was, and how to get rid of it -- it was, essentially, the cauldron of Bran. It animates dead within a certain radius. If nobody's dead in range, it kills someone and animates them. If there's no victims present for an entire day, the radius weakens, and the cauldron loses power, but for each victim taken in this method, the cauldron grows in power and the radius grows. The PCs had to take the cauldron someplace where there were no victims or corpses, and found an abandoned ghost town. They took it to a mine shaft and dropped it down the well, thus ending the problem. While there, they discovered this ghost town was literally that -- a town of ghosts. The place was haunted by an 'over spirit' - the ghost of the town itself, and they had to deal with finding a way to put the dead to rest, as well as exorcise the town itself. Once all that was done, they returned back to the city.
All of this was a subplot. :D
In Shadowrun, the PCs have to deal with hunting down a group of organ-harvesters. They came up with the plan of posing as sellers, bringing in 'defective' bioware parts in the back of an ice cream truck, and offering it for sale to the group. This worked, though the bad guys took the truck too. The PCs wound up hailing a cab, and having the cab follow the truck. This wound up causing them to catch a semi which was used in the 'bait in switch' of the bad guys (the ice cream truck was ditched), and the automated taxi followed the semi. Highway chase ensued with the PCs having to deal with black cars filled with guys using machine guns, and the semi with a rocket launcher.
The most fun the PCs had was me playing the AI driving the car for them.
"Warning. This taxi is under attack. Please remain calm. Lone Star has been informed and will respond in 30 minutes."
"Warning. The taxi door is open. Please close the door. At this speed it is not safe to exit the vehicle." *taxi closes the door finally*
When the taxi was hit by the missile...
"Warning. This taxi has been critically damaged. I am pulling over and another taxi has been called to bring you to your destination. The vehicle you have requested to be followed is currently being tracked. Have a nice day."
The PCs finally got to the truck's destination, and discovered it is a warehouse. They got a team ready, broke in, rescued 40 hostages, and watched the place burn down around them as they escaped.
Currently, they're in Detroit, dealing with one PC's contact having vanished, and discovering this involved sheddim and wraiths... the area the officer disappeared in is a spike point, contacting the horrors, and they'll need to close it down. This is, indirectly, related to the gang that the police officer was investigating. The PCs are discovering that corpses possessed by spirits are no fun at all. Fortunately, my players know that in my games it is better to run away, regroup, and come back prepared for the threat at hand. If they were your typical 'gun-ho' type, they'd have died a few times in my game.