1. The twist on a crank shaft under load. I've heard that stock Chevy 350's with a few power adders can twist a crank shaft up to 20 degrees. You should be able to see the journals bend each time the cylinder fires. A 350 on a dyno with a plexi oil pan would be awesome.
2. A rocker arm floating under extreme revs and maybe some bending/twisting of valve train components and springs. Again a cut away of a Chevy 350 would be perfect.
3. An engine "throwing" a push rod under heavy revs. I would love to see the final blow that bends the rod.
4. Maybe some engine destruction like valves hitting pistons, breaking a connecting rod, slinging a rod out a block ect...
5. In the LeMans series the Ferrari's makes a god awful noise when down shifting at high RPM's, Its a beautiful thing to hear. I would love to see/hear what is coming out of the headers when it does that in slow mo.