Similar to this: I raised a seed round with a deck that was (deliberately) just black Times New Roman text on a white background, plus a few screenshots. The product was also deliberately simple and rough around the edges.

I stole an idea from Joel Spolskey and made beta features in the app have graphics that were literally drawn in crayon, to make it clear they were unfinished and to make it easy to test changes.

Investors liked the deck. It made it clear that what mattered was the content, not the presentation.