“ The PCs are hired by undead to rid their village community of an invasive necromancer.
As the PCs make their way, wherever they are going, they spot two zombies. The zombies approach but before the cleric can turn them, one starts throwing coins at the PCs while the other pleads with them, unable to pronounce the letters 'L' and 'H' due to some missing gums. 'Peeth issen...no 'arm...coin...peeth issen!'
If the PCs don't slaughter the two zombies immediately, they will eventually come to learn that the two were chosen to find help by their brethren. The zombies want to hire the PCs to rid their community of an unwanted pest. An opportunistic necromancer.
Apparently, a small benign community of undead have taken residence in an abandoned village, living out their undeath as peacefully as the undead can. Recently, a malicious necromancer has invaded the village, and plans to enslave the entire populace with his malignant spells, raising a small army.
The PCs must battle the vile necromancer, even as he animates the very folks who hired the PCs in the first place, to slaughter them.”
“ You come upon a ruined building in the back section of a city park (or other out of the way area of the city). The ruins are fairly overgrown. All that is really standing is a doorway and its frame. If you pass through the opened door, you travel to a different world. If the door closes, there may not be a doorway back to get you back.”
“ In a crowded marketplace, a man is standing on a soapbox, orating. Some of the crowd are cheering, some hissing, some standing around saying 'I can't hear a bl**dy word he's saying'. It's a hustings for an election. The PCs can either leave, or stay and listen. If they do the latter, then they can vote too, and they might get quite involved in the cheering. Depending on who wins they might get quite involved in the post-election brawl too...
There are numerous possibilities with this encounter: the PCs might end up talking to one of the nervous candidates before their speech, and offer encouragement and support. Of course this candidate may well turn out to be someone with outspokenly unorthodox views, and the crowd don't take kindly to s/his supporters. Or maybe the seemingly innocuous candidate turns out to be a complete racist, and the PCs wander off embarrassedly, pretending they weren't talking to this person five minutes ago.”