GMing this one in an Eberron campaign:
The players: Vel (human ranger and expatriate pirate from the Lhazaar Principalities), Corden (rogue, scion of House Orien), Corden's poor cleric companion, and Vanity (Vel's dinosaur companion).
Vel and Corden are transporting the body of Aric d'Tharashk to Korth to be raised in a proper Church of Vol, after he's died in a duel in Aundair. Now, while transporting the body on the lightning rail, the party has already been beset by a band of Valenar horsemen looking to take the body. To make a long story short, they COOPERATE with the train robbers, go with them, and escape with the body cross-country when orcs attack. After sneaking through the countryside to the border into Karrnath, Corden acquires the coach that's been reserved for them and, only a day behind, they get on their way.
Now, the corpse is hiding an artifact inside it (unbeknownst to the party), and the only thing masking it from popping up on every wizard's radar was the sarcophagus that the body was in. Which, of course, was left behind in the cross-country escape.
So they get stopped by the Karrnathi Customs Officers, who would like to check out the coach. After some dissembling, Vel figures the proper action is to whip the horses and high-tail it out of there. So the coach takes off at a high rate of speed, with the cleric and dinosaur inside, Corden on the roof firing a crossbow at the pursuing Customs officers (mounted on horseback) and Vel urging the horses faster and faster with successful Handle Animal checks.
The border town was designed like San Francisco, my idea of a stereotypical town on a bay. Complete with large hills and sudden turns. Well-telegraphed, mind you, but still unwise at high speeds. Rushing down a hill, the horses are running at breakneck speed and Vel is burning Action Points to maintain control.
GM: "Okay, there's a T-junction up ahead. Left or right?"
Vel: "Right! We could see the exit to town that way and we'll be through the gates!"
GM: "All right, at a flat run, pulling a coach, on a well-kept street, going downhill - I'll call it DC 14. Make your Handle Animal check."
Vel: *rolls a 1* "Burning an action point?" *rolls a 1* "Oh, fudgesicle (edited for Eric's grandma)."
Corden: "Fudgesicle?"
Vel: "Modified... 7?"
GM: "One of the horses throws a shoe and stumbles. The harnesses snap and the horse is run over by the coach in the chaos. Handle Animal check of DC 16 to keep control of the other horse (I was being overly generous here, I think), DC 16 to regain control of the coach."
Vel: *rolls a 2* "I'm out of Action points. Modified 7?"
GM: *sigh*
Corden: "Oh maaaaan..."
Figured that at the speeds they were going, to treat it as a fall at pretty close to terminal velocity. Coach runs over horse, goes airborne, meets wall of shop at high rate of speed.
Vel - reduced to -17 HP. Thin red paste
Cleric cohort - reduced to -24HP. Thin red vapor
Vanity - thrown clear at *1* hit point
Corden - rolls a natural 20 on Reflex save, flies through second story window and onto bed, breaks bed, reduced to 6HP.
Body of noble? torn to shreds in the crash
That kind of killed the campaign right then and there.