I was doing a presentation about various bombs last year and crashed PowerPoint by copy-pasting billion laughs in a slide. Simple but extremely effective.
Not sure what is worse: that MS has Powerpoint interpreting randomly pasted XML, or that they do not have handling for excessive memory usage beyond crashing the whole program.
https://en.wikipedia.org/wiki/Zip_bomb
The billion laughs XML attack is also lovely in its simplicity.
https://en.wikipedia.org/wiki/Billion_laughs