Most of my on the road encounters were the Festering Fields style on the road encounters but still:
The PCs come accross a attacked wagon train as the sun begins to set as they approach a bunch of oozy goopy men run out and jump them (Acid Shamblers). As the PCs begin to kill them a dark cloud begins to rise from the ground (its the Bane Cloud that created them coming out to play).
Bane Clouds are great... because its Con damage it seems really scary but the PCs aren't in real danger. Since they do one after another its easy to adjust the risk by leaving more time between battles to heal or letting the BC come in early.
A cloaked knight on a hopless quest (IMC it was 'destroy the undead in the festering fields') he's helpful but spooky.
He's actually a Hollow Knight, he's broken with the other HKs over their "withdrawl" from the world. He also knows he's fundimentally a crusader and so he's given himself a crusade to occupy the rest of eternity. He's upfront about being on a quest for Corean (make it good and absurd sounding), knowledgeable and does stuff like give out maps, make suggestions for safe routes to go (AKA railroading) etc.
He's also great Deus Ex Machina later.
I really liked the Alchemist's Eerie in the WotC web page under short adventures. When I ran it there were a few problems but you should check the site. In addition to actually having maps and stats its a good source of innovative ideas.
(all I have time for now)