Wyverns swoop down, snatch the wizard's familiar for a light snack, and fly off!
The characters encounter traveling priests of Ilmater (FR) or Rao (Greyhawk), who proselytize them.
A lone assassin from a death cult (think Thuggee) stalks the group, hoping to find a person on their own (to bathe or have a rest stop or what-have-you) and strangle them from behind.
"The Midnight Peddler" from
Tome of Horrors.
A gnome has created a huge, golem-like walking suit (think steampunk mecha) and is taking it for a spin.
A press gang from a local town or the kingdom attempt to "recruit" the PCs by force.
A small, surreal traveling circus troupe is putting on a show that is creepily applicable to the quest the characters are on (see also
Rosencrantz and Guildenstern are Dead). Also, one of them is a werewolf.
Fairies abduct the most attractive PC and carry them off to the seelie court for a night of revelry that will last 20 years if they others don't come to the rescue.
A king's rider coming the other way, riding like a bat out of hell, and mortally wounded. It's iffy whether he'll get wherever he's going with this message that was important enough to pay for with his life.
-The Gneech
