Here's one I've used more than once, with different groups.
Harvest festival. PCs, being well known heroes, are invited to officiate at various games.
There are brewing competitions, an archery competition, tests/demonstrations of strength like team tug-o-war for the sailor types, caber toss, horse racing, as well as some lumberjack events.
There's going to be a disturbance, an attack of whatever kind you see fit.
In one of these, most of the party ended up entering the archery competition. The 1st prize was a small medal worth maybe 5 gp.
The PCs burned through potions, scrolls and finger-spells like crazy trying to win that little prize.
The "odd environment" part of this scenario is subtle: Who will admit that they came to a party in anything less than full armor, with all their weapons, a full pack and with all of their common "Going adventuring" spells already cast?
The second part is, they have to deal with raiders who aren't interested in standing and fighting heroes. Instead the Orcs/Goblins/Pirates/whatever are running wild, trying to loot the field, take prisoners and maybe even raid the nearby town.
While the PCs will have area spells that can drop the small-time foes by the dozen, there are civilians in the way, people they need to protect.
In one group we had a player who loved fire. He had Chain Lightning, which is made for this situation. Instead he threw Fireballs, Incendiary Cloud, Wall of Fire, and every other AoE flame spell he could think of. He absolutely loved it, and didn't hesitate to fry bystanders, so long as he could rack up a real body count.
The civilians? "They can get Raised later." was his off-hand response. He did more damage to the people and the festival grounds than the raiders.
And that's how *not* to handle a situation like this.
