One of the best spark plugs I ever heard of was literal, but my friend needed to get special permission to do it.

She teaches chemistry, and on the first day of her first class she'd been in there for HOURS setting up a simple four step Rube-Goldberg thing. When the kids sat down, she set the thing off, and it ended with a hydrogen balloon going BANG. Got everyone's attention, and into the silence she announced that by the end of the year, everyone was going to be able to explain WHY and HOW each of the reactions they'd just observed happened.

It was great. The kids were interested, engaged, and she had something she could tie everything back to for the year. Each step of he chain turned up in labs.

Don't know if it's the sort of thing you're looking for...but I always liked it.

G