In an RPGA module, there was a fight with some kind of cold-fire beast. It had a breath attack that hit bunched up characters. The kicker was that the room, a large one, was sectioned into 4 quadrants, and at initiative 0, 3 of the 4 quadrants would burst into cold-flame. Every turn the "safe" quadrant would move around the room counter-clockwise.
There were 4 switches on a central altar in the room, which ended up turning off the flames, but the 4 switches were behind locked panels, and in the four corners of the room were 4 statues which contained a key, so you had to grab the four keys, and ensure that you unlocked the correct side with each key. While all of this is happening, you have an ice wurm beating the crap out of you. So you can try to kill it but you have to ensure that every turn you dont end up in an unsafe zone or you'd take a bunch of damage.
That fight kept everyone moving and shooting, while the defenders tried to keep the wurm in the center of the room to avoid having to move too much and provoke attacks of opportunity. It was a really fun fight, and I've thought of running my own encounter with perhaps lines on the floor that ignited in a pattern or something of the like.